to me, it's been totally worth it. i was lucky enough to be working at Apple when they introduced .Mac, so they gave all the employees accounts the same as their @apple.com account, so it's just my last name. best email address i've ever had.
but it's not just the email. i use the iDisk more than i thought. i'm a designer & when i need to get a large file to the printer, i can throw it up on my .mac page, send them the link and they can download the file through their browser. we have a +/-3MB limit to files going through email here at work & it's nothing for me to have a 40MB ad or poster.
the iSync has saved me a couple times, too when i forgot someone's # or email, i realized that my work computer synced w/ my home computer, so it's already in my address book.
photos may not me a priority for you, but it's REALLY cool if you want to share some photos of say, your dog or your new place w/ people. just create a photo album in iPhoto, pick a theme, hit 'publish' & it's done.
but if it's solely for email...prob not worth it...