Lag is gone as much as possible considering it is a mobile processor. I never experienced a ringer delay with my TP1 but there aren't any issues concerning this with the TP2.
I don't know why you would need a facebook app. Just use opera. This thread gives info on how to get in browser flash support (
http://forum.xda-developers.com/showthread.php?t=544770). First on phone in browser flash option. Skyfire loads the flash on another computer and sends it to your phone.
Though there are many much better IM options you can even use FB IM (
http://forum.xda-developers.com/showthread.php?t=480365)
Pretty much anything is possible with WM. You just have to take the time to learn how to make it all work.