Must admit I'm a fan of HTC Smartphones, currently have a Touch HD (aka Blackstone) and before that had a TyTnII (aka Kaiser).
Have run TomTom and Memory Map on both using the builtin GPS reciever with no problems
Only had the Touch HD for a month, nearly went for the Touch Diamond 2, took me a month to make my mind up and while the Touch HD is a slightly older model it has a bigger screen which swung it in the end
My Lada driving laning buddy has a Samsung Omnia Windows Smartphone, MM works a treat but so far he has failed to get TT working with its builtin GPS