I upgraded from the Hero to the Nexus S
The Hero was a laggy mess, that bordered on unusable. It essentially does nothing better than the Nexus S other than LED notifications. The voice quality is substandard as well.
HTC sense is a bloated mess that offers some ease of usability by eats up memory and processing power, dragging down android's true performance.
It's not even close, the Nexus S stomps the Hero.