A week ago I upgraded my laptop's hard drive, and since I had to reinstall an OS anyway installed an Ubuntu Jaunty daily on it. The installation was painless and straightforward. It went very, very smoothly - somewhat different from the first time I installed Ubuntu on this laptop a year ago (just to be clear, that first time was good too, only now it's better.).
Network set up was easy - much easier than it was under Hardy, as was installing all my familiar apps and settings (apt-get FTW!). My one complaint at the beginning is that compiz somehow got slow. Switching viewports was suddenly very jerky. I would blame my old laptop but it worked just fine in Hardy. So I assumed that it would be resolved in the future, and it did. Compiz now runs even better than I remember it did under Hardy.
Oh, and I also took the chance to use ext4. I don't really notice any difference to be honest but I'm a noob so don't take my word for it. It's apparently going to be standard in the future for Ubuntu so I figured I might as well get a head start.
Overall, I think Ubuntu is getting better each release (I skipped Intrepid, though). Jaunty looks solid and I totally recommend people new to Linux to try it out.