I had previously tried Beta 1 for a short period of time, but as was to be expected it left me quite unimpressed. Beta 2 was different though, as it was touted as a real preview to the final OS release, just with all the bugs you can imagine. I installed it on my Thinkpad, and to my surprise after a rather long installation process, the system was pretty much ready to go with 95% of the drivers recognized by the OS.
After 72 hours of amusement and frustration at times, I was ready to give my opinion on the OS. I get the feeling Vista is going to be as much jump as Windows XP was to Windows 98, but definitely no more than that. That is not such a bad thing if you see Vista as the long-needed, evolutionary update that XP needed so badly.
I won't go further on new features as those have been already covered a thousand times before. I will mention though that the public beta 2 is still far too buggy to run as a primary OS unless you do enjoy frustration, several times a day. If you already jumped into the beta 2 bandwagon like I did, then you probably know what I mean, but if you haven't installed it yet but plan to do so, I certainly recommend you set up a dual boot environment and install Vista Beta in a separate partition which can be formatted later.
Which finally takes me to my last ramblings, and that is that there is light at the end of the tunnel. Reports are popping everywhere of a new Vista build (5456) based on Beta 2 and just a couple of weeks older, which seems to be working much better and stably. Although this version is not available to the public but only to selected tester groups, the word is out of the bag, with new 'Aero' cursors, improved application performance (including a previously sluggish Media Center), smaller RAM footprint, less annoying UAC (User Account Control), and an installation process that reportedly can take as little as 20 minutes (as a side note you should be able to upgrade Beta 2 to this new build if you can get your hands on it first).
It's too bad this is not going to be a public release, but it will have to wait until the next milestone (Release Candidate 1). In the other hand, I see a bright future for Vista, hopefully Microsoft will be able to deliver on time.
Update: I forgot to mention this incredibly useful Windows Vista Beta 2 Software Compatibility List.