Lack of multitasking is yes annoying sometimes, yes, but that is really a poweruser problem. Most users don't load web pages in background while playing. Most users will simply not bother with web pages that take too long to load. Given the choice, most users will prefer a snappy UI over a UI that allows proper multitasking. N900 was never snappy, stutters were common, and it would often hang for long times if you had too many apps or browser windows open at the same time. Even for Android there are way more complaints about non-fluid UI than lack of proper multitasking. It is thus only logical for the Android developers to concentrate in developing a snappier UI over improving multitasking.
The fact that Android has given 400+ million Linux computers out in the hands of consumers is one of the MOST AMAZING THINGS ever. But it seems others on FOSS community seem to consider Android a rather unfortunate event, because it's not "Real Linux" or "100% free software" or "because it's not bug free". Err, like Maemo or MeeGo ever is any of those...
It is fair to complain about usability quirks Android as enduser. But if you believe Free Software, you should also see the opportunity the open source parts of Android provides to you fix it to your needs. After all, the point of Free Software is that you don't need to depend on the upstream to fix you everything? Christoph complains that the stock email app is lacking. Android Email app is Open Source (Maemo and N9 email apps are not). Android email has been forked as K-9 Mail. The app lifecycle is fixable allowing you to return from browser to the mail you were at - at least a plenty of other apps manage to do that.
The question is, are we consumers or creators. If we are just sitting waiting to Google provide us a perfect shrinkwrapped Android, we could just as well use iPhone or Windows phone. We should instead see Android as an opportunity - when it's 90% open source, fix the remaining closed source bits like open source 3D drivers and open source replacements for proprietary interfaces.