Has nothing to do with whether the phone is new or a couple of months old, the entire line has problems including models on other carriers. Make sure you have aGPS off, you might be seeing aGPS results leading you to think the GPS is working.
Also read through the GPS thread (Sticky) and you'll see plenty of entries about the GPS issue, it has been beaten to a pulp. JH7 update, according to Samsung, was to improve performance but it had little effect for me. After seeing the results, I started contacting AT&T endlessly and was able to get an iPhone4.
I do miss the Captivate but both phones are good solutions and I needed one that works. I still follow the forum to see how things are progressing along, would like to jump back to Android in the future. It seems like Samsung is once again delaying the Froyo release, which also includes a GPS fix/performance improvement. This could again put folks with 30 day return windows in danger and if I were to be one of them, I would take the phone back. Like the poster above, I wasn't into making 1000 changes or using different ROMs to get results, I wanted it to work out of the box which as it stands today it doesn't. Even the ROMs don't solve the GPS problems.