[Slack3r]

I had extreme lag on my AT&T TP1, I couldn't even use my GPS for trips involving a lot of turns like city driving because it simply wouldn't keep up, and I would end up just looking at the list of directions and following that instead. I only tried Garmin XT though, so I'm not sure if that was a software or hardware issue. I tried various GPS tweaks to no avail.

No idea on the TP2 since I don't have mine yet, but I'll be sure to test it.