$100 at BestBuy. You can also get it at a good discount ($79) when bought with a new computer from Apple. Unfortunately it doesn't apply to Refurbs.
I've been a subscriber for the last 6 years and will renew again in a short bit.
I don't use all of the services, but I do use their Email, data backup and syncing services. Keeps 2 Macs, iPad and iPhone in sync. That's sufficient for me to pay the $7 or $8 a month.
Oh, and the Find my iPhone feature may come in handy one day. I almost used it last Summer to wipe my iPhone when I thought I lost it. I traced my steps back to my car without finding the iPhone. I had the iPad in the car and was going to wipe the phone, but found my iPhone fell down the side of my car seat.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
I've been with MobileMe since it was dot-Mac and before that, iTools (wow - 11 years ago!).
It's indispensable to me. I enjoy the caché of having an @mac.com email address (newer subscribers are stuck with the narcissistic @me.com). I host several websites in my personal webspace for community non-profits and educational organizations. It syncs my bookmarks, email, etc. across devices.
The one thing I *don't* use it for is backup. Too-limited space (especially compared to something like DropBox) and for reasons only Jobs understands, Finder access to the iDisk has been a dog from day #1 (necessitating the use of a WebDAV FTP program like the super-excellentisimo Transmit).
In short - I do recommend it. But I also hope Apple sweetens the deal a bit in the months ahead...
I use it and really like what it offers. If all you need is email and calendar though Googles offerings might work as well and are free. If you look around you can get it much cheaper then $100 though as there's plenty of places (EBay etc) that sell the codes for very good prices. Just make sure you do your homework on the seller.