Took me about 4 months to fully assimilate into OS X from Windows. I'm at the point where using Windows 7 makes my brain hurt if I'm trying to get any productive work done (web developer). The flow and lack of quality development tools drives me bonkers.
However, I'd say that moving from XP to Windows 7 isn't much of a jump. It's largely the same thing, with things in slightly different (but more logical) places.
Basic map:
Start Menu/Task Bar -> Dashboard (though I don't use the bloody thing)
Control Panel -> System Preferences
Run Program -> Spotlight (this combined with
Quicksilver makes a powerful way to navigate your computer)
Program Files -> /Applications
Alt F4 -> CMD Q
Alt Tab -> CMD Tab
Biggest hurdle I've seen is grasping the concept of how windowing works. In Windows, if you close the window, you close the application. In OS X, if you close the window, the app typically remains open. Apps also share a single menu bar at the top - which can take some getting used to.
Once you "get it", OS X is very much easier to use then Windows - especially for work flow tasks. But if you approach the OS with a Windows mindset and expect it to behave like a Microsoft OS, then no, it won't be easier. It's a different philosophy and a different way of approaching the problem of human interface. So yeah, you actually do need to "Think Different" (hate using marketing slogans, but this one is apt).