Samsung just announced that the update currently being pushed to the Captivate -- AT&T's version of the Galaxy S -- does indeed include a fix for the GPS issues that plagued a good many of us at launch. Here's the official word:
An update to improve the Samsung Captivate's GPS performance is now available. Captivate customers will receive a notification on their device that an update is available and will simply need to download the file to update their phone. The updates will be pushed to customers’ devices over the next few weeks.
The update for the Captivate will also improve additional device functions, such as media scanning time, add the full version of Quickoffice and address Microsoft Exchange 2003 policy support.
If you haven't gotten the update yet, you can check from your phone's settings. (And ukulele_ninja in the Android Central Forums notes you can bypass the pesky one-check-per-24-hours thing by changing the date.)