After over a week now of running on the HP MediaSmart Server 3.0 update, I can say the following. I notice very little difference. That's mostly a good thing. I rely on the device to back up my computers without complaint, hold my video and music files and pretty much be invisible. It has remained so.
I had a few bumps along the way. I believe reinstalling the Anti-Virus software kicked off a full scan of multiple terabytes of data which made the user interface quite sluggish - though I didn't notice any issues copying to or from the device. The UI is a little easier to use, but the old one wasn't awful so that's not a huge issue. I will say that it doesn't seem to squawk about problems updating live domains any longer - but that really wasn't something that should have been affected by the update. Perhaps just reloading the OS did the trick on that one.
Overall it was a good move. I'm sure you're waiting for the "but" though, right? There isn't much of one, but my timing was off by a bit. Lo and behold, Microsoft just announced the public "Vail" beta for Windows Home Server. I'm sure it's based on the Server 2008 R2 platform which has a lot of stuff for Windows 7, etc. I wasn't likely to install the beta anyway, but I might have waiting on doing the upgrade at all if another upgrade was so immediate. I'm quite certain that I'll have to pay for this upgrade as well, but it may or may not be a good thing on this hardware so there may just be a device upgrade in my future.
Technology marches on...