Feel the guilt. You should go and confess your sins later. I do understand though. First time Mac Buyers who are PC users end up with huge buyers remorse until they really start to use the machine for a few weeks. Then it seems justified. (either that or the cognitive dissonance sets in)
Enjoy your new laptop, I think you'll like it. If not, you'll find that macs tend to have good resale value and you can sell it.
just be happy that you spent a few more dollars and got a MacBook that will last for years, than cheap out on a PC that will break in 6 months (no lie!!)
take it from me, a successful Mac convert. we had WAY too many PCs before that got viruses and crashed, then my parents saw the light and got us our first iMac, and i've never looked back since!
-iChica