I recently received my complimentary Ubuntu distro CD in the mail. Since I ordered the x86 version, I received a "Live" CD, as well as an installation CD.
Before I installed it, I thought I'd check out the Live CD. I wasn't impressed. Knoppix out-does the Live CD performance-wise by leaps and bounds.
Anywho, I installed Ubuntu Linux on a spare partition and am impressed with the results. Bear in mind that I'm completely unfamiliar with partitioning and was thinking, "This probably isn't going to be happening.", as I had a single partition on my hard drive and had absolutely no idea how to split it for a Linux install. Ubuntu guided me through the process and I figured it out quite easily. Before I knew it, Ubuntu was installing itself onto it's own partition and installed a bootloader to let me select which OS to use upon boot-up.
Ubuntu seems to be perfect for someone who just wants something that is simple and straightforward and doesn't come with a billion different applications that they're never going to use. Though the applications it does come with are pretty robust.
This was my first encounter with the Evolution Groupware Suite - which basically combines everything I like about Mozilla Thunderbird and everything I like about Microsoft Outlook 2003 into one application. From the looks of things, it also has support for Microsoft Exchange.
In my previous Linux experiences, I've found the process of setting up file sharing with my small network to be a bit of a pain. However, Ubuntu configured and recognized everything for me. Absolutely painless.
Speed is decent considering my system specifications. OpenOffice apps take a bit longer to load than I would prefer - but in my experience, this has always been the case with OpenOffice. Doesn't take long for the system to boot into Ubuntu, either.
I haven't really seen much with Ubuntu that has irked me yet. But it has impressed me. So if you've only tried the Live CD - install it. Because the Live CD doesn't accurately represent what Ubuntu can do and the speed hinderance doesn't allow you to fully experience the OS.
Good luck.
Brandon