I just got an iPad2 and am running Slingplayer Mobile for iPhone and iPod Touch (was previously running on those devices). It's fine as long as I switch to SQ mode, if I'm in HQ mode it buffers every 3 seconds or so. On SQ mode I am quite happy with it. I am living overseas and my slingbox is back in the US so I can probably never realistically expect to run HQ mode and not lag, despite fine internet connections on both ends.
The problem I'm having is that if I hook up my Apple AV (Component) Cable to my TV, I am only getting Audio output to the TV when in SQ mode. In HQ Mode I get both video and audio, but have the buffer/lag issue as above.
I guess before I go and buy the iPad app I want to make sure I won't have the same issue...if it works for this scenario I will gladly plunk down $30 but if it doesn't work I'm not touching it and the iPhone app is just fine for me.
I understand that you are having some issues with the SPM application on your iPad2, since the audio/video signal is out of synch.
I recommend you to check this link, in order to get some information that might help you.