I have a TP2 with WM 6.5 and myFaves and can confirm it works flawlessly. No problems at all, minutes are still allocated correctly and all that.I have loaded it all up and got a very nice 6.5 ROM on my phone and i do see that everything is working perfectly. I am pretty much in love with this phone and all the things i can do with it! I feel bad for my Zune HD since im now using the TP2 and bluetooth headphones to listen to music, podcasts, and surf youtube... with my boring desk job, this phone is a must have.
Keep in mind that it WILL remove myFaves from TF3D so you'll have to update your faves through my.tmobile. You might be able to push the myFaves app from the website to your phone, but I recommend against that. The app is a memory hog and you would probably have to go into the start menu to use it, I don't think it would be on TF3D tab anymore