Solid guide Hudson. I just got my Grav/Kin to 40 over the last double xp weekend, and it's tons of fun.
Couple of points where we differ... I prefer lift over crush, especially in the early levels where you are mainly facing groups of 2-3. GD one, lift the second, GD the third, lift the second, GD the second. With luck, the amount of incoming fire is minimized. Then you can move to melee, and use AS, transfusion, etc. Later on you may want to switch to crush.
I agree whole-heartedly with your assessment of Wormhole; it can be an excellent pulling tool, especially later when combined with Singularity, who will happily guard a door and/or watch your back for any adds. Wormhole into a corner in front of your team, Fulcrum Shift, apply crushing field, and you're golden.
I went with flight on my build, mostly for concept reasons, but also for vertical movement, and it pairs nicely with Air Superiority. I held off on Hasten until the late 20's, and didn't really feel I suffered for it.
I fully recommend taking Hasten. Once you've three slotted Siphon Speed with recharge, and three slotted Hasten, it's nearly permanent. You will notice if you miss on a Siphon Speed, and you definitely notice once Hasten drops. It's almost like playing at half speed after that.
Stamina is absolutely necessary. I've thought about spec'ing out of it now that I have Transference, but I find this to be a very busy character. Between applying holds, making sure I hit siphon speed every time it's up, pulling for my team with wormhole, healing responsibility depending on team make-up, hitting FS when appropriate, and throwing out GDF when someone aggros too many mobs, I don't really have time to be continually refilling my bar using Transference. And that's not even considering the calls for Speed Boost. Stamina means I have to apply Transference less, and by the time you get it, most builds have sorted out their end issues already. It becomes a nice top up, not a necessity.
Maybe it's just me, but sometimes playing this guy can be exhausting.
The glaring downside of this build is the complete focus on Smashing damage. At lower levels, it's hardly a concern, but as you get higher, more and more mobs become more resistant to smashing damage. So while there is a potential for huge damage when you Propel after a well place FS, don't get overly excited by the numbers.
Epic Powers of course address this.
There is a significant lack of AoE damage as well, and Epic's fill this gap too.
