Android multi-tasking has been praised for years as one of the best multi-tasking systems in the mobile industry. UI wise, webOS has always been better, because it was much more intuitive, but ICS has solved much of that problem, at least if manufacturers keep using the software buttons and multi-tasking button (which Samsung doesn't do with the Galaxy S3).
iOS took years before it implemented “some” multi-tasking capability, and even now it still only works for a few types of apps. WP7 multi-tasking is also quite poor and doesn't keep almost anything in the background, not even an IM. RIM may have the most advanced multi-tasking system right now, because every single app keeps running in the background, although it remains to be seen, with BB10 smartphones, if that was a wise choice or not for battery life. But even so, Android multi-tasking remains at least a top 2 in the industry.
Unfortunately, HTC seems to be taking that position way down (some even say worse than iOS) with the One X. They've implemented such aggressive memory management that once you switch to a different application, your previous application will be deleted from memory, so if you use multi-tasking at all on your phone, that means those apps will have to load again.
This is not how Android normally manages multi-tasking. Usually, apps stay in memory until there is very little of it left, and only then the “oldest” apps in memory start to drop out, and make room for the newest apps in memory. This allows the user to easily switch between many previous applications without reloading them every time.
Android may or may not need a bit more aggressive memory management, so that if you have 1 GB of memory, or even 2 GB like some new phones will have, it shouldn't wait until you have only 30 MB left to clear up the old apps. But killing them as soon as you enter a new app, seems like a huge, well, overkill. It makes the large amounts of RAM modern Android devices have almost useless, and breaks the multi-tasking experience for Android users.
Here's a video depicting the problem, courtesy of YouTube user wrxdrunkie: