Smooth enough. I usually play in Medium and that runs great. C&C3 in High and that runs great. Why different? Too lazy to change the settings. But always in full res. You should be fine.
OK, I take that back. Didn't seem very happy. Runs on High in Windows though. I guess that's what you get with Cider ports.
Just my opinion, obviously, and I don't know how much time you spend in Windows, but I find the graphical drop to be worth not having to boot into Windows each time I feel like playing.
If you want some extra info on what settings look like what, try this site:
http://www.pcgameshardware.com/aid,...gs-compared-plus-system-requirements/Reviews/
Shows a really good comparison of all the preset graphics options.
Very smooth, unless you have a tank swarm of 100+
Frame drop, 4GB
Seriously, what are your specs? I get choppy on High, but definitely smooth on Medium. I can even play acceptably on Medium with the 9400M switched on instead, and that's a much lower card.