Well, you can't swing a dead cat without hitting an Ubuntu 12.04 review, with pictures, videos, step-by-step instructions and everything else imaginable. So rather than write yet another, I am going to take a different approach - a quick result run-down and a few comments about installing it on the various computers around here. As I have a fairly wide variety of hardware, in both configuration and age, this should cover a lot of different situations, and perhaps offer hope and encouragement to those considering upgrading (or especially those considering installing for the first time), and consolation to those who might have tried and run into trouble.
I like to start with the good news, so I will lump a bunch of these together:
Fujitsu Lifebook S6510, HP Pavilion dm1-3105ez, Samsung N150 Plus, Asus Aspire One 522: All installed from scratch flawlessly, and everything works. Wireless networking using various cards from Intel, Broadcom and Atheros, graphic displays in resolutions from 1024x600 up to 1920x1280 (on an external monitor), using display controllers from Intel, ATI/AMD and nVidia, Bluetooth, and of course all the routine things like USB ports, SD/MMC memory card slot, HDMI and VGA monitor connections, and whatever other hardware those systems had. All very routine.
Then the not-so-good-but-not-terrible news:
Installing from Live USB memory stick is slow. I mean really, really slow. It takes ages to boot even as far as the "Install Ubuntu" / "Try Ubuntu" prompt, and then ages again after you choose one of those options before it is ready to work. The installation procedure is nearly identical to previous releases, but takes many times longer as well. I don't know what they have done to slow it down, but it is amazing, whatever it was.
Also, on the HP Pavilion dm1-3105ez the infernal Synaptic ClickPad doesn't work properly. To their credit, Ubuntu gets it closer than many other Linux distributions, because you can at least simulate a right-click with a two-finger tap, but that's about it. Click-and-drag is a nightmare, if you can get it to work at all, and of course two-finger scroll doesn't work at all.
The really bad news:
It absolutely refused to install on my Samsung NF310 netbook. This may very well be some sort of problem with the computer, but it is worth noting that I have recently installed Linux Mint Debian Edition 201204 on that system, and it was no problem at all. The problem seems to be something to do with reading the partition table, because it never comes up with the question about importing documents and settings from other operating systems, and while the installation processing actually does start, and seems to run through copying files, installing the system, configuring hardware and such, it always crashes when it gets to importing documents. It's not just the import that crashes, either, it must be crashing ubiquity (the Ubuntu installer) completely, because it is left without GRUB installed, so it won't boot.
I tried quite a few things in hopes of getting around this problem, to no avail. I even went so far as to delete all of the other Linux partitions, and the Extended Partition they had been installed in, so the system was left with nothing but the original Windows partitions, and it still crashed when I tried to install Ubuntu 12.04. So I finally gave up on that, and decided that system could be a good test unit for the upgrade procedure. I reloaded Ubuntu 11.10 on it (which loaded perfectly, by the way, so why won't 12.04 load?), and then went to the Update Software utility and selected the option to upgrade to 12.04. It gave me a pretty good explanation of what it was going to do and how long it would take, and that some packages from 11.10 would no longer be supported, some would be removed, some new packages would be installed, and a lot would be upgraded. It then downloaded over 1,300 packages, and set about performing the upgrade. It has been at that for about an hour now, and appears to be about halfway through. Not bad. If it completes successfully, I'll be impressed, and pleased.
Even more bad news:
On a brand new Samsung NP300E5A notebook (so new that I haven't even written about it here yet - stay tuned), with Windows 7, openSuSE and Linux Mint Debian already installed, when I installed Ubuntu 12.04 and told it to put GRUB in the root partition (not the MBR), it screwed up somehow and left the system unbootable. Not good. I was able to fix it without much trouble, and once I got over that it seems to work just fine, but that is a pretty big stumble.
Once it is installed and running, it seems to be quite good. Be prepared to be patient while it is installing, because rather than the 10-15 minutes it takes to install most Linux distributions, it is more likely to take 30-45 minutes. But installation is a one-time operation (or should be in most cases), and once that is done the boot and operation speed seems quite normal. It is well known around here that I don't like Unity, and I don't see anything in this release that changes my feelings on that in any way. But that's just me, and there seem to be plenty of people who like Unity. Fine, choice is one of the major strengths of Linux. I wish them lots of success with this release - anything that hurts Microsoft is wonderful as far as I am concerned, and more power to them.
Update - shortly after I posted the above, the upgrade finished successfully on my NF310. It looks like everything is just fine, and it even kept the configuration for things like wireless networking across the upgrade. Less than 1.5 hours total time. I'm honestly quite impressed.