boxhead, I have a 359 and love it. I have had no problems, and it has gotten better with use (easier starting). I have been looking to find a definitive answer on whether the XTorq on the 455 actually gives it more torque or not, but the 359 has more HP at less weight, so for the extra $$, I think you will be happy. Although one person on another site argued that the power:weight of the two was the same since the 455 holds less fuel and bar oil, thereby making the weights similar. Uhhhh, OK.
Plus, I don't recall if someone mentioned it, but the 359 has magnesium cases, whereas the 455 is metal-reinforced plastic. In the end, I think well worth the small amount extra. I have a PDF file with more info than the owner's manual, but it is on another computer. I'll try to remember to look for it if someone else here can't scrounge something up.