Movement does feel a bit floatier but it hasn't really detracted from my experience. Loved the game itself so far and the DLC store is just there to fleece morons so it doesn't really bug me that much. A minor complaint I have is that I don't like the new loading screens and there are way too many of them. Portal generally had a loading screen every 2-3 test chambers, Portal 2 has one every single chamber. They don't take long but the blackout screen really pulls you out of the game. The old frosted glass/out of focus loading screen was a lot better imho. Anyways really minor things in an otherwise excellent title. There's easily 15-20 hours of content between the SP and co-op campaigns, well worth the $40.
The game doesn't feel like a console port at all either, I barely even noticed the saving message.