I will never say about myself that I know it all.
There's more that I don't know, then what I do know.
But after working nearly 17 years in IT, at an helpdesk of hospital who supports about 2500 people and came from W95, W2000, WXP and soon W7) I do think I am more then an experienced user.
Without doubt I can say that W7 is the best OS created my Microsoft so far.