We have a pro-account at my office with SEOMoz and it does indeed have some excellent tools.
You get much more information via open-site explorer, and they have automatic rank-checking tools which track your keywords in bing, google, and yahoo (as well as how many visits each keyword is sending)
It works excellent as a quick look at where are rankings are, but I always use another third party program to double check their rankings.
The competitive analysis tools are pretty stellar as well - I've come to trust their ranking metrics (MozRank or whatever they call it) a little more than Pagerank.
All in all I would say the subscription is worth it IF your boss pays for it. If he/she doesn't chances are I probably wouldn't use it on my own as there's plenty of free tools that do the same work.
But as a white-hatter (well mostly

) they do offer excellent tips - I check up on their blog regularly and can honestly say their articles have provided me with the knowledge to get a fair share of white hat backlinks.