that would really depend on what your using your card for, if your a musician and do recording then you may really want the true 24bit recording. If you watch a lot of movies on DVD then you may really want the added 6.1 capability (and the THX cert.) You may also like the fact that it supports DVD audio. Or is compliant with Microsofts Media 9.
for most folks, I would have to agree though, depending on when you purchased your audigy, it would probably not be worth the upgrade right now, although depending on when the new microsoft standard is adapted, this may change. If I had bought an audigy a year ago when they first came out and was now considering an upgrade I might be tempted to go for it. Since I currently have a Live!5.1 I am certainly tempted towards the Audigy 2 (particularly the platinum version, gotta love the thought of that remote)