(and I have a Droid b/c I like the open platform and, yes, I would buy it again) -
Whatever the iPhone does, it does very well. With that said, it only does what Apple allows (unless you jail-break it) and even though the upcoming OS will allow multi-tasking, all apps may not be capable of it. There are certain restrictions Apple is placing on multi-tasking to ensure that the iPhone/iTouch performs to their standards. If an app doesn't meet those restrictions, no multi-task for you!
The original poster asked about an iTouch, I think. When Apple comes out with the next version of software, you will have to buy it for the iTouch but it will be free for the iPhone, if Apple does as it has in the past.
If you buy an Android phone, I would make certain it has at least Android 2.1. That is the latest/greatest OS for 'droids so you won't have to worry about upgrading the OS and any potential problems when you do anytime soon. Also, I love my Droid but I "may" run into problems soon with the memory. I don't have the long & short of it yet but there is a memory limitation for apps and it looks like I may run into that (but I haven't yet so I don't know if this is a real problem or if I'm just looking for things to worry about).
To me, Android is free-er and looser than Apple so you might have a little more of a learning curve. But Android users are fanatics (like Apple users) so they are very supportive (unless you badmouth their phones, in which case the villages are on their way to your house w/torches & pitchforks yelling "Kill the Beast!"). You have to ask around to find out about things like doubleTwist, Swype, HandCent, etc. or to learn about putting shortcuts & folders on the homescreens.