Concerning the first 2 posts, things are not exactly like that. It seems that hd3000 performs better for newer games, since drivers are focused on them. Comparing the 2 last mb air models (that is, 2010 and 2011) shows that 2010's nvidia gpu can do better on most older games while 2011's hd3000 seems to be slightly better on new games (like portal 2 for example). So, you can expect mb air 2011 to outperform the older models as new games come out.
In any case, having worked with both of them myself I can assure you the 2011 mb air is very much faster on the desktop graphics (mission control responds significantly faster). And that's the most important issue for me, since playing games on a mb air is an exception, but desktop graphics are always there.
As for games, generally is not a good idea playing 3d games on a mb air anyway, since the internal temperatures are going to crazy levels (don't take my word, just download istat pro widget and check), so for me is not an option as it lowers laptop's life (since none would get a mb air for games as a main job).
