I'm not really sure whats wrong with your TP..But i'm not having any of those issues with mine. The GPS works great, I get a lock within 30 seconds. With Scotts ROM loaded on my phone its a lot faster and mine NEVER crashes. If I were you I would have a look at these two threads before you return the phone.
http://forum.ppcgeeks.com/showthread.php?t=56777
http://forum.ppcgeeks.com/showthread.php?t=49933