i have a tom tom that i bought in december last year and it is AWESOME! i love it! so far it has been right on in pretty much every situation. plus, they have updates pretty much all the time (although I still havent updated it yet).
The map updates are available annually at a cost (like Garmin). The POI and stuff like traffic camera locations are updated more frequently, not new addresses & maps.
I'll have to say though, that my next GPS will be a TomTom, even though I currently have a Garmin C320. I want spoken street names and bluetooth.