1. for ocassional gaming, how much better is the 2010 than the 2011
The 2010 is much better. It's mainly a windows drivers issue though. When running Skyrim in windows 7 64bit the 2010 will get around 10 fps more than the 2011 with the same graphic settings in the same in-game environment. it's around 25 compared to 35 fps on low settings. But it's playable on both though. They'll both run most games fine with the exception of games using new high end graphic engines like battlefield 3, the witcher 2 etc..
2. how much hotter and louder are the fans in the 2011 compared with the 2010
I don't know about the 2010, but the 2011 is very, very loud when handling games and the fan will also kick in when using apps like Skype. When the fan is running 6500 i think it's one of the loudest laptops i've owned. Luckily it only reaches this level when gaming or doing relatively heavy media processing. I think it's because of the integrated graphics solution featuring only one heatsink and one fan. It doesn't get very hot at the enclosure though, only the cpu temps go above 90, but I believe sandy bridge processors are better designed for operating at these temps than the core2duo. The 2010 has two fans so i assume it would be more quiet and maybe cooler.
3. how much longer does the 2010 battery last
The battery life of the 2011 is great. for me it lasts a full work day with word, mail and a couple of windows in safari open. It really depends on how much the fan is spinning, so i would imagine that for cpu and gpu intensive tasks the 2010 would last longer, but then again the core2duo is actually a very old laptop processor. And in a few years it will not be able to handle web browsing without making the fans run at full speed.
I bought my 2011 because of thunderbolt. Since the airs doesn't feature usb3 until next year, i thought i've just buy one with thunderbolt and hook it up to a small dock. But it's been a year and basically no peripheral has been made featuring thunderbolt, and i'm starting to worry that the industry will skip out on intels venturous endeavour at least for mainstream usage. By god, i wish i owned a laptop with usb3 or just firewire800 for that matter. My thunderbolt connection is like any other thunderbolt connection just sitting there doing absolutely nothing. And I think it's beginning to stare at me.
Hope this was helpful
Best regards
Sam