I'm not touching it until it's at least SP1 - call me paranoid but I like having a stable OS 
Surprisingly its not crashed yet - even with me running all sorts of home rolled software on it, tho I wouldnt use it for any deliverable just yet.
Definitely good as a second OS - currently theres no option to dual boot and the hardware requirements are pretty thirsty. In order to run the aero UI you need a graphics card which supports directX9.0 and has at least 128Mb of dedicated memory. Other requirements are for 1Gb of RAM and at least 1Ghz processor - tho I expect it might struggle with this. The memory is a definite must tho, its currently running at about 600Mb utilisation with only IE7 open.
Aside from the fancy graphics theres plenty of new stuff under the hood. Searches are lightening fast (and they even search the contents of emails), the ghost service from Win2003 has been incorporated to automatically back up all your files in case you delete something by mistake. Security and programme access has been completely redone as has the underlying file system.
The main office components have had a complete face lift and now have xml based files. Theyre actually zip files and you can view the contents by just renaming from .docx to .zip
.Net 3.0 (previously WinFX) has just been released so I'll be giving it more of a hammering over the coming weeks
