Yes, the availability of software has been an issue for one friend - but it all depends on what you use your computer for. She loves cross-stitching and wanted to use some of the software that was available for creating patterns - only available for the pc. So that's what she got.
I use mine constantly for photos - iPhoto makes it sooooooo incredibly easy to download, post to our .mac web site, email and print. So I'm absolutely in love with my iBook - especially with wireless internet and printing through the Airport. And iMovie is great too. Oh, and iTunes and the iPod - not only can the iPod hold music, but it all hold information like a PDA and you can download your digital pics to it if your card gets full.
Now I know there are caparable things out there for pc's, but it is also about being user friendly and what you are already familiar with. I could get all the pc stuff, but there would be a definite learning curve!
First, think about what you need it for, and work from there.