strange... I haven't noticed too bad of call quality on speakerphone. This is, of course, in comparison to my former non-smartphones. You ought to take it in and see if you can compare it to one in-store to see if it's just your phone or what. You could also compare it to the DX to see if that one is any better. I rarely use speakerphone so I don't really notice. I did just listen to pandora on the speaker of my fascinate last night while I was cookin some stuff on the grill. While not ideal obviously, it wasn't HORRIBLE...
Battery life... well... sucks. And from what I hear from everyone who has a smartphone, that's just how smartphones are. For me, I was tossing back and forth the incredible and Fascinate and one of the tipping points for the fascinate was battery life. Well, now that 2.2 has come out, it really blows. REALLY BLOWS. I'm not sure if the DX is any better but it may be.
TBH though, you may want to go with the DX just based on the lack of support from samsung/verizon for the fascinate. That is my biggest complaint of the phone really...