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That's really a matter of opinion. Some people think it's worth the money, others do not. In other words, it's not really a question we can answer for you.

Assuming you've already familiarized yourself with .Mac through Apple's website and you're still on the fence, I recommend signing up for the free 60 day trial, and perhaps purchasing a one year subscription after that. If you find it's not worth it, there's no need to renew.

Also, many have reported that you can find .Mac licenses cheaper on ebay.
 
It really depends what you want it for - hosting your mail and website? Backing up over the web? Synchronizing multiple Macs?
 
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