I have a 15" MacBook Pro and I love it!! I've never scrapped on anything larger, though, so you might feel the difference a bit if you change screen size. I have thought about getting an iMac, but I don't think I would like losing the amazing portability of my MBP - especially the ability to take it to crops or on vacation, etc. That would be harder to do with an iMac, though not impossible.
I don't think you will regret switching at all! And, there is a growing community of Mac users here that are alway really helpful with questions.
