Here's a youtube video of a guy that was able to get his hands on the Evo for a day...from what I can hear, the speaker on the phone is good quality...it won't be anything like the TP2 in terms of dual speakers but this phone is way different in design...
HTC Evo 4G Audio and misc stuff
also here's another preview of the Evo 4G..and some of the things it can do.
HTC Evo 4G Demo