Lets see...
Dimps usual lack of attention to physics noticable in the water running segment (When Sonic jumps all momentum is completely reset)
The music is just a really bad sounding remix of Aquatic Ruin (Which already wasn't exactly a great song to begin with, IMO) EDIT: Okay I guess that isn't the real music. The music still reeks of MIDI.
The stages still appear to be prerendered garbage instead of true Polygons (The logs, folks)
Its [tornado fang]ing Aquatic Ruin. [tornado fang] Aquatic Ruin.
I would say its the Sonic Cycle all over again, but to be fair I don't think anybody was anticipating Sonic 4 E2 after E1 failed to impress.
The Special stages don't look too bad though, Tails doesn't have his movement delay from S2 anymore, and it kind of reminds me of 3D Blast's Saturn Bonus stages as opposed to Sonic 2's rendition.
Aside from the underwater segments and certain traps, Aquatic Ruin wasn't bad at all. And since it's the first zone, it's not going to be as difficult as AR was in Sonic 2. The logs aren't prerendered, if you stop the video at the right moments it's definitely polygons. And while the whole physics thing will probably never be perfect, at least they're improving from Episode 1.
Also, the music does bug me. Jun can't seem to capture the catchiness and character of the Genesis-era music with these new songs. A perfect comparison is to this Stardust Speedway remix, which
is used in the game but sounds so radically different from the rest of the soundtrack:
[youtube]http://www.youtube.com/watch?v=7hFSWi2msGo&feature=player_embedded[/youtube]