Ok. My thoughts.
Install:
Very painless. Also much faster than the previous beta I had. It took around 20 minutes to install for me. That said I installed 32bit this time around.
Explorer:
I find the new explorer shell to be extremely good. It does take some getting used to I'd admit. Only thing I found lacking was the 'up one level' button, but the bread crumb bar does this anyway (and more). Browsing large folders is an order of magnitude faster than XP. General navigating is instant too. Everything is snappy and fast. I have a 20gb downloads dir, with ~10k files. Navigating to it is instant, and all the data is there in a second or two. On XP this can lock up for upto 20 seconds.
The data density is much higher than XP explorer (which is good!). Virtual folders seem very good, and promise great things. The file system indexing was surprisingly fast too, much faster than the last beta I had. No more bugs with the folder view either.
Explorer has yet to crash on me.
I also prefer the toned down colour scheme they have now (for things like meta data down the bottom, etc)
desktop UI:
not much has changed between betas. Maximised windows are no longer black, which is shame. I really liked the black look. Media player 11 beta on XP looks awesome, yet looks really quite bad in vista. I have to say glass is overdone. The gadget chooser for the sidebar in particular is pretty bad.
Overall the UI feels a good deal faster than the last major release. No more sudden frame rate tanking.
The start menu is growing on me, however the lack of icons next to Computer, Network, etc means you generally have to read the buttons, which isn't good. I'm still not 100% sure the search in the start menu is setup right. Ideally I feel it should only search what’s in the start menu, not the entire PC. If you type 'N', it should filter to all things starting with N. I want to type 'N' and press enter for notepad (this will happen the very first time you boot, but from then on you need to type 'notepad' before it appears in the results... ???)
They fixed the fade in *horray*
I'm still not 100% sold on the UI. Pretty much because of the skin. Technically is fantastic of course.
I also really don't like the 'araura' style of the login UI. Not at all. Doesn't mix well at all with the rest of the UI which is quite subtle (except glass). If you could set a background image here I'd be very happy.
The sidebar is actually really quite useful now too.
Windows update impressed me a lot. It found drivers for my TV tuner, creative live ultra webcam (which officially does not exist according to creative). It downloads fast and installs painlessly.
Media centre seems improved.
The advanced command line tools (aka monad) are really quite cool. Haven’t had much of a play myself, but been shown it. Looks very much linux-like in usability. Word is that there will be a command-line only version of Vista Server too... (kinda ironic
Office 2k7 impressed me. The new UI is very slick (although it's still not 100% implemented in all apps). Although I haven’t actually sat down and done any serious work with any of the apps, I get the feeling that I'd be more productive than office on XP. Which is a good thing.
The new adaptive application caching thingy-whats-it also showed up. After a few hours random stuff I went to open Excel to show someone. It opened in around half a second. I was stunned.
The big let down so far has been IE7. Several factors here, one it's still beta. And very obviously so. This forum is unusable as everything flickers like mad. Second, it's still all GDI rendered, so full screen scrolling (16x12 res) was noticeably choppy. Unfortunately I don't see it being all that likely we will be seeing an WPF rendered IE anytime soon (sigh).
The access control stuff is still a bit annoying, but having the shield icon on buttons/programs requiring auth was a nice touch. Over all it's no where near as annoying as the previous beta I had. I'm sure it will get better but it is a lesser of the evils I guess. Odly clickonce applications don't require auth.
Overall I give it high marks. For a beta it's quite stable, and also remarkably fast. The big problem is most people won't see what’s gone on underneath. Knowing a bit about what new things vista brings for programmers (eg, winfx) and the like pretty much makes it an utter no brainer upgrade for me.