This is something I saw on another website so it's not my idea but it really seems to work. Try downloading an app called Home Manager and setting it to auto kill htc sense. Then reboot your phone. This has greatly improved my multitasking.
I wonder what the side effects of killing the process are...
If you rooted your phone, here is another fix:
[MOD][23/05/12] Improve your One X multi tasking using script - xda-developers
The 1x has a lot of potential. However according to many reviews and a little research, it appears that sense is still holding it back. I've heard read many reports of the OS lagging due to sense. The web browser isn't that good, but you have the Google Crome option. The frame rates are actually less than that of the Galaxy S2, but that because of the screen res. and last but not lease, crashes. My last HTC phone had these issues, which is why I'm hesitant to buy this phone. I'm thinking about waiting and seeing if Google will produce a flagship phone that will utilize AT&T's LTE network. I would like to experience the pure Android experience this time around.
Anyway, has anyone with the 1x experienced any of these issues?
My ATT One X is great. GPS is fantastic, quick accurate locks and nav. BT voice dialing was disabled by HTC (i called) but i fixed that by rooting and installing voice dialer apk as system app. Heavy graphics programs like Sky Safari run smoothly. No crashing of apps however i have had sense reload a couple times. Link handling is crippled (likely due to the patent issue with Apple). Multitasking does seem to be crippled somewhat but that is being fixed. And free RAM runs low compared to other devices I own/have played with that have 1gb of RAM installed. But I think all these software issues will be resolved with custom ROMs. Hardware wise the battery has been fine, but the button locations are a PITA for a phone this size, the screen is gorgeous and so detailed, the recessed front camera is a dust collector.