If you visit the AT&T Forums for the Captivate, you'll quickly see that this issue has not been resolved.
However, the problem wasn't so much that GPS didn't lock, but sometimes the accuracy left something to be desired, as in GPS showing you're one street over from where you actually are.
That said, I've never had an issue with my GPS. Accurate.
Same with random shutoff. Still happening but Keep Alive on the Market seems to have resolved many of those issues, although there are those who are continue having issues even with Keep Alive.
That said, neither myself nor my bf have experienced any random shutdowns with our Captivates. (Well, I did once, when I had a task killer installed. But once I uninstalled, this problem never recurred).
Personally, I love the Captivate and would recommend it.
Read the
CapFaq for all you'll need to know about the Captivate to help you make a decision.