I'm disappointed in the 630 (8GB/512MB combo is something I'd like to get rid of, for one.) ,but two things sprang right in my face that convinced me that this would be my next phone:
1. The price of ~$160 (considering taxes and the obligatory you're-not-a-Samsung tax here, you're seeing that even out to ~$200 here.)
2. The battery, which was good enough from my point of view.
Of course, I also like the design.
What really pushed me over the edge, however...is that I broke my 620's display, rendering it unusable.