It's largely a result of muscle-memory, you will find the interface you use the most to be the best, simply because you've learnt to use it without thinking. This will happen on any interface switch, and is probably the main reason I found Vista to be a step backward from XP.
I'm considering switching (back) to a Mac and any switcher needs to factor-in this element. The OS will be awkward for the first month until your motor systems relearn the movements needed.
The whole process is actually made worse by the fact that you can easily run your old Windows programs on your new Mac, as you end up switching back-and-forth between two different paradigms and disrupt the learning process. So if you plan to use the Windows programs you know on your new Mac, you should add a couple of months to the time it will take you to feel comfortable with the Mac interface.