As you can see, we've made quite a few changes. Here is a (hopefully) complete rundown of everything that has change in "Amirite Version 4" as we're calling it. In no particular order...

Discussions

Originally Amirite was designed as a platform for simple questions with yes/no answers. Since its beginning we have expanded upon that to allow custom voting options, or to have no voting options at all on posts. That opened it up to allow all different kinds of content to be posted. We noticed people started using it for general open-ended discussion about a topic, or simply just socializing.

So now we're making that an officially supported kind of post. It's now called a "Discussion". These are posts that have no voting buttons and are generally open ended questions or discussion topics. Discussions have everything else that regular posts do - they can be loved, commented on, and shared.

The "conventional" posts that do have voting options are now called "Polls". You can choose to see just Discussions, just Polls, or a mix of both with the buttons in the header (click on the logo to get to the Home Page which shows a mix of both).

Posts

'Post explanations' have been replaced with the 'post body'. When you make a post you'll see this new box to type in. What you write in the first box will always be shown when you see a post in a list or anywhere else. The second box - the body - can be seen by clicking the "Read More" button on a post. This allows Discussion posts to have a short title and the main content visible when you click on the post.
You can now use markdown formatting in the post body. See http://www.amirite.com/formatting
You can now add or change the link on an existing post.
You can now add or change the image on an existing post.
The "vote to be on the homepage", and "suggest for POTD" features have been removed. These turned out to not be that useful as they all do the same thing - to indicate that you really like a post. Instead you can use the Love button to do that. We will now use the number of loves a post has to pick posts for the homepage or to be Post Of The Day.
Favourites are now called "loves".
Added an option to use the classic 'Yeah You Are' and 'No Way' voting options.

Custom Voting Options

The "Other" option no longer gets automatically added to posts with custom voting options. You can of course still add an Other option if you feel it's appropriate. For many posts an "Other" option didn't make sense, which is why it is no longer added automatically.
The default colours of the voting options are now less ugly. You can also pick a custom colour for each option by clicking on the coloured dot while adding/editing the options.
The entire text of the voting option is now shown, instead of being truncated.
Voting on posts with custom options now counts towards the 'vote on x number of posts' achievements.

Famous Thoughts

We have removed the Famous Thoughts section, because nobody used it! (Fun fact: only 652 thoughts had been posted since its creation in April 2013, while 35,000 other types of post have been made in the same period).

Comments

If a comment is deleted either by its poster or a moderator, the replies will still be shown. Previously it appeared as if lots of comments had been removed, but really it's because they were replied to a comment that was deleted so they had nowhere to be shown on the page. The same goes for comments from posters you have blocked - you will still be able to see the replies.
Comments are now sorted by score (up / down votes). The "Top Rated Comment" section has been removed because that comment will now be at the top anyway.

Topics

Previously there were far too many topics to the point where they became too specific and useless. We noticed people were assigning random topics to their post, which further reduced their purpose. This is understandable as it became too awkward to actually find an appropriate topic for a post. So we have significantly reduced the number of topics to a small set of "core topics" so they are much more usable again. You can see the new list here: https://www.amirite.com/topics
Posts can now only be in one topic as it was rarely useful to have them in multiple and it makes it faster to make a post.

Moderation

Profiles

You can now use markdown formatting on your profile to add headings, tables, links, and photos. See the formatting options for more info: https://www.amirite.com/formatting
The colour theme you have chosen for the site (from the Settings page) will now also alter how other users see your profile. For example if you choose a purple theme for when you browse Amirite, your profile will appear in purple to other visitors.
Added the ability to upload a photo to be shown in the background of the header on your profile.
Your avatar, theme, and header background image now shows across all sections of your profile - about, posts, comments, achievements etc.
Updated profile stats and design.
Removed limit on the amount of times you can change your username.

Chat Room

We have a new public chat room. This is a feature we used to have a long time ago and was well received. It was replaced with a "private group chat" system, which nobody used, so we have brought back how it used to be. It's available at http://www.amirite.com/chat

Messages

Waves

To replace the ability to leave messages on another user's profile we have added the "Waves" feature. These are short publicly visible messages that appear on your profile. Try it out: https://www.amirite.com/user/anthony

Notifications

Notification now arrive instantly instead of a delay before you see them.
Notification are now better organised by what they about. For example notifications about comments on a post are now shown together.
When you click on notifications about comments the entire page won't refresh if that comment is already on the page. You'll just be taken to the comment.

Achievements

The Post of The Day related achievements have been fixed.
Some old achievements have been removed.

Miscellaneous

You can now pick any colour you want as your background for the site (from the Settings > Appearance page).
You can now use an animated gif as your avatar or profile cover photo.
All images in comments/posts/messages are shown as a preview and you can click them to view the full size. This not only cleans up how comments/messages look and is faster to load, it also fixes a security issue we have run into in the past with displaying images from third party sites directly on Amirite. For your safety, any content shown on the Amirite site now only comes from our own servers or trusted third parties (mostly Google).
Added a new support ticket system for the contact page to keep track of support requests.

Behind The Scenes

Under the hood the site has undergone huge changes. In fact we created a completely new site from scratch and imported all the old posts, comments, people, and everything else.

Starting from scratch allowed us to only add what we need, and lose all the unused features and strange patches that have accumulated over the years.

The original site was created in 2009, and mostly rewritten in 2011. The tools and technology available (and the experience of our developers!) has come a long way since then. We created a new site using modern technologies. There are countless bug fixes and improvements to how the site operates.

What Next?

We're definitely not finished improving Amirite. This new site is just the beginning of a new platform we can develop with new features, better performance, and changes based on your feedback still to come. The old site has become unmaintainable so we had to build this new site to continue to improve.
I know there will be lots of feedback both positive and negative and I'm looking forward to hearing from you all! Please use the contact form at https://www.amirite.com/contact to get in touch.