My phone would sometimes lag when sending texts after being idle for a while. Or it would lag when opening up applications.
I've read that some other people are having lag issues as well. It really wasn't a big deal, but it bugged me enough. I downloaded that BBSAK program and wiped the device, re-installed the OS and restored everything to my phone.
It hasn't lagged on me once yet. It may in the future, but who knows.