From srb2.org and the SRB2MB:

Quote Originally Posted by Mystic
It’s been a few months since we updated, so I guess it’s about time we came back with another reminder that yes, we are indeed still working on 2.1, despite all reports to the contrary. As always, click on the images for a higher resolution shot, and everything here is subject to change by release time.


Here’s a shot of the final room of Arid Canyon Zone, showing the alternate path that didn’t exist in 2.0.X. A lot of sections throughout the game have had similar modifications to try to fix the difficulty curve and make it more reasonable.


Those who have been playing SRB2 for some time will no doubt recognize Aerial Garden Zone, a hidden stage in 2.0.X. It has been updated slightly in visuals, including a simple sky ripped from Sonic Advance, as well as tweaked for difficulty and bugfixes. Because of the removal of Red’s room in CEZ2, there is a new method for unlocking AGZ in 2.1.


2.1 includes a new character selection option: Sonic & Tails. Just like the classic games, this causes Tails to follow you around, eternally trying to catch up while getting hit by everything for your amusement. If you have set Player 2 controls up, you can even take control of him directly to fly yourself around.


2.1 supports tallpatches, which allow extremely large graphics to be inserted into the game without issue, as demonstrated in this test WAD of an extremely large, single-patch texture built out of various images of the Yakumo family. The things in the foreground are also using sprites beyond the old size limitations.


Techno Hill Zone, Act 2′s reworking for 2.1 continues onward, reworking the level to play better with the new slime and updating the visuals. This screenshot demonstrates the new look of the slime room at the end of the stage, along with some new content in the background. Please forgive the HOM, as certain parts of the stage haven’t quite gotten cleaned up, and the stage is very much still a work in progress.


Here’s another screenshot of THZ2, showing off an all-new outdoor area, demonstrating the usage of skyboxes in a more dramatic fashion. As with the other screenshot, this area is still very much a work in progress.

As a reminder, if you’re looking for even more 2.1 information, check out the Version 2.1 page on the Wiki.
Quote Originally Posted by Mystic
We've had a few bad 2.1 threads recently, so this is an administrative notice that this thread will be aggressively moderated. Discussing known information and speculating based on that information is okay, but don't go on tangents or make baseless speculation or absurd claims. To start off the thread, here are the answers to the questions I KNOW half of you are dying to ask yet again:

1. There is no release date. Asking will not change that.
2. The netcode is still just as shitty as it was in 2.0.X.

Since that's already answered, we don't need to go over it again. With your cooperation, we can actually have a lively, intelligent discussion instead of senseless begging, and I'm pretty sure that's what you all want too, not just me.