Hi again Alan,
I would pretty much have to agree with all that's above. It really must come down to ROI and for someone who is just running a single site, then the decision you're faced with is how much up-front investment you are prepared to make and whether you are prepared to sustain that investment in the long term.
While all of that is obvious, I thought I would share the one thing included in the SEOmoz Pro subscription that I think is potentially the most valuable and perhaps the most under-utilized by Pro members...
1 Free Private Question per Month!!
Yes, I made it bold and underlined it because this is the one feature that could provide you with the professional input that changes your business completely. The pity of it is that many members completely forget about their private question. Maybe this is because they don't realize it actually means you can ask a question and have it answered by a member of the SEOmoz Staff or Associate.
Yes, that means you could actually have the help of someone as awesome as Dr Pete, John Doherty, Jen Sable-Lopez, Keri Morgret, Casey Henry, Michael King, Gianluca Fiorelli, Dan Shure, Cyrus Shepard and many more...
Even Rand Fishkin?
Yes. Even Rand answers private questions. The fact is, your question will be assigned to a person on the SEOmoz team who has the skills and experience to best help you.
Obviously, your private question needs to fit within the subject categories available here in Q&A and you should be careful not to waste it on something you could as easily get answered here in regular Q&A. With that in mind, I would consider the potential value of such a benefit to your business and think carefully before giving it up.
Hope that helps,
Sha