Installation was unchanged from 11.04, so much so, in fact, that it even says "Welcome to Natty Narwhal" :P
As with Natty, installation was quick and easy, with the option to download updates in the background as you go. As before, personalization questions were presented *after* installation had already begun, which saves even more time.
The login screen has changed a bit, and now looks really snazzy, with a stylish dot motif in the background. There's an option to select a Guest Account, along with the option to use the new 2D/non-accelerated Unity desktop, which I believe is powered by the Enlightenment libraries. This 2D desktop supports true transparency, which is nice.
The jockey-powered "Additional Drivers" utility automatically found the binary driver for my wireless, which is the nonstandard Broadcom chipset option, so all I had to do is tell it to activate it. CORRECTION: My wireless driver was enabled, but not working. On returning to jockey, the driver was listed as not installed and if I tried to enable it, it would give me the error:
SystemError: E:Unable to correct problems, you have held broken packages.
This suggests that my packages were installed, but somehow got messed up. To fix it, I had to find out which packages for my chipset were installed, by typing:
dpkg -l | grep roadcom
(notice, I searched for 'roadcom,' which will catch packages with both 'broadcom' and 'Broadcom' in the title and/or description. This is important, as the bcmwl-kernel-source package will not show up if you search for 'broadcom' alone.) Then remove them entirely by typing
sudo apt-get purge [package names from the previous command]
Reboot, then try the 'Additional Drivers' utility again. It should successfully enable the driver, then you can reboot again and everything should be working properly.
If you got the standard chipset, it should use the open source driver by default. The default video driver is the Gallium-3D-driven open source driver, but I chose to install the proprietary fglrx driver from AMD via the driver utility.
Audio seems fine and my HDMI audio hardware and output were both recognized from the start. The headphone jack also properly mutes the internal speakers when headphones are plugged in, which is an improvement over my experience with Natty.
Waking from suspend seems fine, too, though hibernation still seems to be a no-go. :(
The default email client is now Thunderbird, which works well with Firefox, the default browser, and the default music client is now banshee (this may not have been a new change; I can't really remember...).
The built-in search tool for Unity is much improved, with little icons down at the bottom of the window for choosing whether to search everything, just files and folders, just applications, or just search your music collection.
Everything seems to be fine so far, a solid improvement over Natty on these machines. I'll post back if I run into any problems. If you have any questions or experience any problems, post a comment!