The latest drivers don't show a whole lot for the HD 4890 and HD 4870 X2. As for the HD 4850 we see performance drops in many games and by a good chunk. For the most part we wouldn't recommend HD 4850 users upgrade to the latest set of drivers.
As we've mentioned a few times already, we don't have any release notes, but there's no doubt going to be the usual array of bug fixes in games and applications which is always a good reason to upgrade when we don't see a performance drop.
With the driver being WHQL certified already we don't doubt that the 9.5s are going to show up in the next few days. For the most part it looks like they'll be worth the upgrade if you're sitting on a higher end ATI card.
As always, we don't test all cards and games, so if you find any pros or cons with the driver suite make sure you leave a note in the forums.