All systems: The next version of Ubuntu's Linux desktop, due out April 28, will feature some really big changes, including a very new desktop shell running Unity, a "Test Drive" for apps, and a default LibreOffice installation. Try it all out and see how it runs with the public beta.
The best way to try out the beta is to load it onto a USB stick for no-install launching — we recommend UNetbootin for that task. Download the proper ISO (the x86 "Desktop" option in most cases), plug in your USB stick, then launch UNetbootin and choose the option to manually point to an ISO.
If you've been using Ubuntu 11.04 "Natty Narwhal" in its alpha stages, or have put in some time with the beta, tell us what you like, and if the Unity desktop has won you over, in the comments. Ubuntu 11.04 is a free download for any system.
Ubuntu 11.04 Beta [Ubuntu]