The GPS is fine on the Charge in my opinion. Yes, it does lock slow indoors, but the TB wouldn't lock at all. The Charge locks plenty fast outdoors (2-3 sec usually, 15 sec max), whereas the TB would take anywhere from 2-5 minutes. All in all, it's pretty much on part with my old Touch Pro2 in terms of GPS, which was also fine in my opinion.
However, I do miss having the Garmin navigation software and maps available, which I had on the TP2. Google Navigation just isn't (nearly) as accurate, and also requires a data connection at all times.