Hemsky had elite acceleration, average to slightly above average top speed. Average might be the poor word for it, he was faster top end than the average NHL player, but compared to his top 6 peers, I would certainly call average an apt word.
If he had a strong top speed he would have had more break-aways in his prime, and he wouldn't have lost fasted skater competitions to guys like Horcoff or Stoll who were in no means speedsters. He never really blew by kids with shear speed, more of a come in slow and change gears faster than they can. Thats not really speed, it is more is acceleration. Hemsky got from A to B faster than most players, but if you gave most players enough time they'd overtake him.
But, we are talking about a guy I havn't really watched play in years, so i could be mis-remembering.
And agreed, Larsson's lateral movement is beautiful.