PC or Mac?

I have a had a trusty Dell Inspiron 6000 laptop for more than five years now but it's starting to show it's age now - possibly because of the number of people using it.
My daughter has her iTunes on it and is constantly downloading video and other applications and for some reasons shuts down when it gets bored or just freaks out. I've always shied away from Macs until we started using one in the office a couple of years ago when we bought two of them for the designer - desktop and laptop.
Now I am considering replacing the old Inspiron either with a new one or a Mac.
Now I know Mac as a brand has some real evangelists who really get into everything that is Mac - from laptops, to iPhones (I have a Blackberry) and iPads. And up until recently, I have resisted joining the Mac cohort but may now join them.
Any thoughts people - should I abandon Dell for Mac?