I have only had the Captivate for one day, I swapped my iPhone 4 for one yesterday, and I must admit I really am in love with it. I have been with Apple since the 2G phone, but since the first day I got the 4, I honestly was disappointed with it right out of the box. Didn't like the feel, dropped my first 3 calls, and the proximity sensor put the 4th call on hold. Sure the screen was out of this world, the camcorder and camera were top notch, but it was just sort of underwhelming.
I spent 8 straight hours yesterday playing with the Captivate. The ability to customize anything you want really is refreshing. I didn't like the built in keyboard layout, so I just downloaded a new one. This seems to be true for pretty much every aspect of the phone.
It does seem to drop bars when I hold the bottom of the phone, especially in my house with bad signal. But, it is more like my 3GS, doesn't drop a call. So far, even with no bars, I have been able to get data transfer.
So yeah, cool story bro, ect, ect. Just my experience.