The beta release of Ubuntu 10.04 came out about two weeks ago, and I've had a chance to play with it off and on. You can run it from a USB drive and make no changes to your computer, which is quite nice from a testing standpoint. My thoughts are a little late, since beta 2 is on its way and the final release is due before the end of the month.
As a starting point, I think Ubuntu is great because out of the box, its a full featured operating system. It comes with an office suite, photo editing software, a music player, software to make backups and more. More importantly it runs great on older hardware, extending your investment and it runs great on new hardware. And its free. Support is as easy as searching a forum. Free, great and runs on the computer you have right now.
Gwibber - I'm excited about the updated Social Media application, because the latest versions won't run on what I have installed now.It has nice UI and can update and view updates from many different social networks. It even shows responses to your friends' statuses on Facebook!
Latest Firefox and OpenOffice - the latest versions are included in this release. I was able to keep them up to date via standalone installs, but the standalone installs lacked the polish and integration that the Ubuntu team puts on the. This gives OpenOffice support for the Microsoft Office 2007 formats (docx, pptx, etc).
The UI is pretty slick, too. The new purple color scheme isn't quite my cup of tea, but it does look nice. I also noticed some transparency in the in the terminal window which was a nice touch.
The new software center has a nice look for managing what software you have installed. No need to find a program, download it and install it, using software repositories its a one stop shop!
There are a few disappointments, but not major things.
GIMP, the Gnu Image Manipulation Program, is not included by default, but that is easily remedied by installing from the software center.
I'm a little saddened by the fact that Pidgin is not the default IM client. Its replacement, Empathy has some cool features, like integrated video chat and more desktop integration, so I'll give it the old college try. It currently doesn't support Office Communicator, as plugins for Pidgin do, but its open source, someone will build one.
Probably the biggest issue, as many others have noted is the close buttons on left and side of the window. WTF? I think its a ridiculous move, but its open source and all configurable by the end user. How To Geek has a simple post on how to fix it, which will probably be the first thing many users do.
A friend of mine says that Cisco VPN not currently working in this release and has had issues with his Verizon card. These are important things, but this is just a beta release, so I'm sure that in a few months these will all get cleared out.
All in all, Ubuntu 10.04 will be a nice upgrade and is a Long Term Support release. There are a few more releases before the final version comes out and I think the Ubuntu Community has done a great job with the Lucid Lynx version.