The only one that appears to work currently is Multifl0w. Ryan Petrich says ProSwitcher doesn't support 4.x at all, which is the same thing I heard from the developer of Circuitous. Multifl0w is really not my favourite solution, but it's the only one working. (Albeit barely, it really doesn't like being in landscape mode). I vastly prefer ProSwitcher, although Circuitous would have been better than nothing. I haven't mucked around with jailbreaking since last year so I haven't been following if there are improvements on this front. Are there any other app switchers that are working on the iPad 2?