I beat the story. It took me about 12 hours. If you tried to hardcore speed run it, I doubt you could do it faster than 9-10. I only got side tracked doing hearts once, other than that I was going from chapter to chapter in between getting mounts. The only time it was gated was getting the Springer mount. You needed to get the canyon jump for the raptor to get to that area. The skimmer was only needed for one part, and the jackal is just extra for story... it seems a good bit of MP are gated behind it's abilities though. Once you get the Springer a wealth of MP become available, and you get one for each part of the story you do. You never really feel impeded by these. Each of the 3 mounts after the Raptor require a renowned heart to do, they offer the unsummonable mount and get you to practice its abilities to complete the heart. If only they'd have a CC heart. I'd say the Raptor is my favorite, its upgraded jump covers a lot of distance as long as you aren't going up hill. The Jackal is pretty neat, but seems situational.
The story was damn good. Bravo to Anet for the voice acting, and the writing. Canach and Rytlock were epic with their back and forth banter. I had a lot of good laughs. Steve Blum and John DiMaggio were on top of their game. You'd never be able to tell it was Spike and Bender. There was comedy, drama, suspense, surprises, and action. There was a large amount of variety as well. It wasn't a rinse and repeat "beat this enemy, defend this gate, talk to this person". Some of the achievements were pretty shit though. They either required 2 play throughs to do the opposite thing you did before, required a mount you wouldn't have had access too yet, or they were only soloable with a high DPS class. With how long the story was, it would be tedious to grind this. But I'm glad the story was long... and that the final boss wasn't bugged like Mordy.