FWIW, I am on my second Captivate, during my 30 day evaluation window.
My first one, i tried all of the above settings, and even left 3G geolocation on to prime the ephermeris for the local almanac.
Didn't matter, no lock.
The new one, I get lock on 7-8 satellites from a pool of 9-10. Accuracy is 16.4 feet. This is persistent through a hard boot, and without wireless networks enabled.
Now, I have heard some say that GPS worked perfectly when their Captivate was new, and then it got progressively worse.
Just throwing out my data points. As long as the GPS functions work and my WiFi functions (though it is still 1/2 of an ipod touch, but still better than the earlier model), I am happy.
Now, my Captivate seems the equal of the EVO 4G I had, plus it is much more pocket-friendly and portable.