.Mac is great and for me good value for money as it saves my time and has many features I use on a regular basis :-
I publish 6 web sites from iWeb to .Mac very easily and quickly.
I publish Photos and Videos from iMovie and iPhoto.
All of which resides on my 10Gb of space (of which I am only using 2Gb at the moment.
I have a .Mac mail account as my main email address. It has great junk mail filters and I access it on my iPhone, iPod touch, Web and Computers.
I sync my Address Book, Calendar, Bookmarks, etc, etc via .Mac to my 2 computers, both in sync all the time.
I use .Mac to access the Back to my Mac feature which lets me access my desktop from my laptop when away from home.
I access my Bookmarks and Address Book while at the office
I use the free Backup software to backup key information to my .Mac iDisk.
I use iDisk to transfer large qualities of data to my friends.
For me it is simply the only way to do all the above seamlessly and with no fuss or pain. Yes you can do it for free or less from various suppliers, but for ease of use it can't be beaten.