Well, thanks to forum bugs, first review was lost. So, trying again...
There were elements to this AP that were definitely interesting and novel. However, they can't counter balance the disappointment I feel with the ending of this AP.
We got wind of what was to come midway through Book 5. The party is destined for a soul destroying TPK that you aren't coming back from, barring GM leniency on using a sidebar mentioned in Book 5. But you get to be heroes!! You stop the BBEG!! Your names will be remembered forever!!
Well no. The campaign just ends. The BBEG isn't permanently destroyed. The world of 1E is ending and 2E will appear, what, 10 years down the road, with our BBEG (and/or his minions) as a part of it. Hope your players haven't invested much their characters.
So - in a nutshell, subscribers pretty much just paid for a 6 installment AP aimed at setting the stage for their 2E rollout. Yes, I'm that cynical. Return of the Runelords is part of this too - but frankly, that at least had some options for permanently ending a lot of bad guys - or at least the ones Paizo didn't want to bring into Golarion 2E. This one? No such luck on permanently finishing off Tar Baphon.
1E was a fun ride. Too bad it goes out on what I feel is a real low note for an AP. It could have been so much better.
Paizo should have left their edition world changing for a 2E supplement or a PFS scenario and not used this AP as a way to do so.
Tyrant's Grasp seems pointless and hollow precisely because that is all it was - window dressing setup for 2E.