The device software you have is the offical AT&T version, at this time.
All the carriers are testing the next generation OS, when they are satisfied it will run correctly, with a minimum impact on their customer support system, they will introduce it for future sales. When it is official, you can download and install it with confidance.
Some carriers have already approved it, you can find link to their version a the top of the Curve Discussion forum. The catch is, AT&T customer support can not help you if you encounter problems. We can.
However, if your device is company owned, you should not modify it without approval.
The upgrade is well done, all of your setting, data and third party programs will be carried over intact. It is still a good idea to have a current backup, just in case.
reed has already explained it pretty well. it kinda blows though for consumers, since some other carriers are already running more updated OS. so the user loses out.
but hey u can always do an upgrade by yourself. plenty of help files to teach u how to use other vendors' OS.