Yes, I just discovered that the HTC Hero (Sprint) has excellent voice dialing capabilities. It does an outstanding job of recognizing my voice. Just hold down the call/send button until you are prompted to speak.
It doesn't dial directly, rather, it gives you a quick choice of what it thinks you just said. Then you're one finger tap away from calling the intended person. I like that much better than my old phone, where it would frequently misinterpret what I said and start calling the wrong person.
You can use these voice commands at any screen and for more than just dialing. For instance, if you have an application called "Checkers" - you can say "Open Checkers" and it will put that at the top of your screen as a choice. Tap it and go! Very nice!
The problem is that you have to remember the name of your apps. Sometimes they are not simply names "Checkers".