A quickie tech review here:
I've been an enthusiastic Ubuntu user for several years. I've been running Linux for... wow, I guess close to a decade now, crazy! It's come a really long way... when I first installed, the switch to 2.4 was really big news. I initially used Corel Linux, a shockingly short-lived brand, but one that put a premium on ease of introduction. From there I moved on to Mandrake, which I liked for its best-in-class installation and cutting-edge repositories. I abandoned Mandrake around the time it was renamed Mandriva - not due to the name change, of course, but because I had been hearing relentlessly positive things about Ubuntu, and I was getting sick of the untar-configure-make-make install dance leading to the Dependency Nightmare from Hell. apt-get sounded too good to be true. It was true. I became a believer, and have never looked back.
Jaunty Jackalope is the latest official release. Ubuntu has a phenomenal release schedule, one that seems to be directly inspired by Agile methodology and that provides a great testimony to how to build quality products: publish on a schedule, and if you run out of time, drop features instead of rushing them or pushing back the deadline. Anyways, they come up with new releases every six months. Each release is regularly supported with updates and patches for 18 months. (Every fourth release is a Long Term Support release, meant to be more palatable for businesses, that gets three years of support on the desktop and five years on the server.) So, with the regular patches, what's the deal with the six month releases? Partly it is to act as a baseline, so people can easily download a single well-known image instead of a bunch of amorphous packages. But it's also important because significant new programs or changes may only be introduced for a new release.
All that said, Jaunty is, at first glance, nearly indistinguishable from its predecessor Intrepid Ibex. Even the desktop background color looks the same. Don't let appearances fool you, though - Jaunty carries the kind of improvements that users most crave, like faster start times and more responsiveness. Booting is noticeably quicker than it used to be, and program switching goes really smoothly.
There are some application updates that should please people - they have the slick new Open Office 3, and are finally making it easier to use non-Open-Source-yet-essential items like Adobe's Flash player and nVidia's video card drivers.
I'm actually pretty limited in what I use Ubuntu for - Firefox, Wine (currently playing Oblivion mods), Eclipse (for software development) and the terminal (for general fun). Everything runs at least as well as it did before. Wine still isn't perfect - there's a weird glitch in Oblivion that resets the in-game sounds to muted every time I launch it - but it seems to be faster and more stable now.
Each new release of Ubuntu makes it better and better. I can unhesitatingly recommend it to people who mainly use their computers to browse and do other light tasks. It still has a ways to go at making it easy to run Windows-only programs, but even there, if you're willing to invest some time into making it work, it feels like just about anything is possible. When you look at Jaunty running side by side with Vista, there's no question that Jaunty is friendlier, faster, and more powerful.