Theres plenty of screenshots and news articles about the Windows 10 interface, but why have those when you can have pony themed ones!
Heres what I got from looking around the preview build:
Most of the tablet interface is disabled when your on a regular desktop PC (huzzah!), or just gone for good. Though its still kinda... weird here and there. For instance when searching for the configuration panel it gives you the 'settings app' as the first result which is basically the rather badly dressed down tabled version of the configuration panel.
The aesthetics are... simple would be the most generous way to describe them. Its not ugly or anything but it does seem rather bland, and the only things you can change are the main color (the dark blue in the screenies) and the font size on the title bars, the latter of which requires a reboot for... reasons.
You are eventually supposed to be able to remove that tile section in the start menu, but thats not implemented yet. I tried getting it gone so thats why mine is all weird and empty, on a fresh install its full of those weather/news/random stuff app tiles, which I never really use tbh.
It runs Horsegame and Dwarf Fortress (which are really easy to just copy-paste and run), runs fine as a virtual machine (I am running inside my current windows 8 installation). Haven't done much extensive testing with games but compatibility is bound to be very similar to Vista/win7/win8.
There is quite a lot of bugs left over though. The release is supposed to be in June so I guess the MS developers don't get much time off now
All in all I would say its an improvement over windows 8, though frankly they could have just updated the back-end on windows 7 and have the thing everyone actually wants...
Now... should I try to run it on an ancient notebook with 512mb memory and some weird VIA CPU I never heard about, just to see what happens?
Edit: Hmm it can still run horsegame with just 1gb of memory. The fun things with these virtual machine is that I can just give it whatever specs I want. Lets see it if runs with 512mb and 1 CPU core heheheh!