First opinion - I like it a lot - it has several of the good parts of Vista [Yes Vista had good parts.] - but, it is also much faster and cleaner.
I migrated from 32 to 64 bit - that required a reformat and a clean install of my boot hard drive. The system itself is up and functioning fine, but many of my application programs now have to be reinstalled. [All data files are on other physical hard drives in the box - nothing has been lost there.]
It's an interesting exercise - one that I do just infrequently enough that each time I have to relearn how to do it. But, so far, relativly painless, and I'm quite pleased with the result.