I had the HTC tilt and diamond, which were made by the same people as the G1, but used WM6. The phones were nice, but the touch response was a bit off at times. Not sure if it was WM6 being slow or the phone itself. The Tilt was super bulky, but had a full qwerty keyboard that slid out AND a touchscreen, which was nice. The Diamond was much lighter and smaller, but had the onscreen keyboard which took some time to get used to. It also didnt hold up to getting run over by a cab....
I also had the BB Perl for work and now the BB Curve. the Curve is 1000000 times better then the perl. having the full qwerty again is amazing. Also with GPS, etc it is a very nice phone. I actually only carry my curve now (partly do to the unexpected end to the diamond, and partly due to the fact the the curve rocks). I havent gotten to play with the storm at all, but BB software seems to be more responsive then WM6 for sure. Not sure about android or iphone.