i have the touch diamond and i must say the GPS in it is flakey as hell, sometimes taking a minute to get a lock, sometimes it wont lock at all. the advice i have seen on this is tio disable incoming beams and turn off bluetooth. this helped me slightly and i hope it can help others, but i cant rely on it as my main GPS device... id be sitting in the car for ages waiting to set off to get to work
on the other hand, when it does work it is fantastic, with the va screen making tomtom look much better than on my tomtom branded GPS device in my car.