To get what I dislike out of the way, in GFZ and THZ, crawlas are littered all over the friggin' place, but in all of the new zones, they don't appear once. I embrace the fact that the new levels don't use them as a crutch for difficulty due to lack of enemies, but the transition from Techno Hill to Deep Sea is still very weird in this sense, and I think it'd be a good thing if the Single Player campaign had a little more consistency in enemy usage in that regard. The save system is fine, but as I've said before, continues need to play more of a role in the game now that there are no more difficulty settings. Camera appears to have some issues, mostly minor. Netplay is also still unstable, but I don't think I need to go on about that. Stuff's going to be a bitch to port, but that's just granted, and it may be a good thing in some aspects.
What I like about the new version outweighs the previous paragraph easily. The Single Player is fresh and enjoyable, and gives me plenty of emblems to hunt for whenever I feel like it. 2.0 has a ton of new thing types that I'm quite eager to take advantage of, and the new enemies are creative and pretty well thought out for the most part. There's a wide variety of vibrant textures that can easily be used to add a fresh new look to SRB2 mods along with the new scenery. As unstable as netplay is, it's clear that a lot has been done to enhance it both on the technical side and the general gameplay side; error logs, IPs listed along nodes, consistency failure correction, and for me, sock errors have become rare (if not nonexistent) on this laptop of mine, and that alone is an absolute blessing to me; and then the game modes themselves are much more polished, match and CTF incredibly so, thanks to the new system. One big thing that supported the game balance and made Knuckles and Tails quite a bit more enjoyable to play as was the pair's altered stats, as well as the occasional alternate path in circuit and SP mode. I use all three characters so much more now, and I can even outrace some Sonic players in circuit with other characters (though I haven't gotten first with them yet :P). Along with improved music, there's a bunch of remixes included and old tunes (some that I didn't even know about beforehand) brought back, meaning I have a lot more favorites to choose from.
All in all, two thumbs up. You guys obviously have some kinks to work out both online and on the single player campaign, but I'm still impressed with what you've done to the game. 2.0 has a lot of features that 1.09 needed badly, and the whole product helped to make an otherwise stale 3D platformer an enjoyable experience that I play daily once again. Keep up the good work.
EDIT: Also, tumbleweeds are just damn cool.