The new taskbar style has grown on me quite a lot after using it for a few hours, I was abit unsure/confused by it at first but now I can see the point behind it. I like the way you can access things by right clicking the icons. For example if you right click the WMP icon it shows you frequent playlists or if you right click the explorer icon it shows frequently used files/folders, right clicking IE shows your recent history etc, so it's really like having the equivalent of a notification icon for those programs only you haven't. Saves on clutter and makes things tidy as well as functional.
I also like the way the Documents, Music and Pictures icons intergrated into the start menu are no longer just folders they are libraries, so you can add multiple folders to it in properties and when you open "Music" it shows the contents of all those folders, nice and convienient.
To say its a leaked BETA yet I've been able to get drivers for everything except my soundcard (so I've just switched to onboard which works) and I got all my drivers straight from Windows Update. I've also had no major stability issues and it's been very quick so I can conclude that Windows 7 has got off to an impressive start and it's looking good for the final release.