I'd say that the Captivate has about average reception. It really isn't the greatest, but as far as I know, that's due to the power rating on the antenna and its location.
It has a mild case of "Death Grip" as well, though all phones do to some extent.
Really, it's all a matter of perspective. If someone came from an iPhone, they say the reception isn't bad. If you come from a Blackberry, you'll want to throw it out the window. I was very disappointed with the Captivate's antenna coming from a Bold and before that a Curve. I guess I was driving the Lexus of phones without even knowing it.
I spoke to an Engineer (Not Customer Support) at Samsung, and he claims it was an effort to conserve battery life. A higher power antenna would pull more juice- and the Captivate already has a mediocre battery at best. What they should have done is include a high power antenna and just put a software controlled current limiter on it so you could give it more power if you wanted to.
Alas, the antenna in the Captivate is not one of the better ones. Once my warranty is up, I think I'm going to try replacing the antenna circuit. It's not going to be easy, nor will it be anything a non-EE should do.