I always wanted to make a Father Time themed grav/kin, but lost my craving a bit when they introduced one as an NPC in the Ski Chalet.
Kin is always in great demand for teaming.
Grav is a little . . . odd. Propel, Dimension Shift, and Wormhole are very unique powers and need some getting used to, both as a user or as a teammate with one.
Propel is a very cool animation -- you summon anything, including the kitchen sink, and hurl it at people. It does great damage, but things are usually dead before the animation is done. Use it as the opening shot or only against hard targets.
Dimension shift is an AOE enemy cage or, a targetted phase shift, if you prefer. It's almost better as a griefing tool against your teammates since anything you hit with it cannot be damaged until the effect expires. It can be useful to neutralize a spawn when too many have been aggroed, but most players leave that power on the shelf.
Wormhole has a lot of critics as well, but it's a wonderful and unique power. It is an AOE teleport foe with disorient and knockback. Most of the complaints come from players who knockback npcs out of range of the rest of the team. But if you use it wisely to place groups in a corner, or to add a few more bodies just before you use fulcrum and a blaster unleashed a nuke, you will be loved.
Wormhole is also a source of fun. There is nothing quite like sending a large pack of skulls or hellions into orbit and watch as it rains men.
50s: Inv/SS PB Emp/Dark Grav/FF DM/Regen TA/A Sonic/Elec MA/Regen Fire/Kin Sonic/Rad Ice/Kin Crab Fire/Cold NW Merc/Dark Emp/Sonic Rad/Psy Emp/Ice WP/DB FA/SM
Overlord of Dream Team and Nightmare Squad
I don't know what one's definition of great is, but I have a grav/kin that I thoroughly enjoy.
She's very versitile and since grav has more than one power I'm not very fond of it leaves me free to expand on the kin side which although blooms a bit late is a huge boost overall, especially when you hit FS and transference.
oh and who doesn't love sings? 
Spines/ D A lvl 50 Scrap, stone/wm lvl 50 tank, Kat/reg lvl 50 Scrap
Grav/Kin lvl 50 Cont, Fire/Enegry lvl 50 Blast
Warshade lvl 50, PB lvl 39, nightwidow lvl 50, crab lvl 42
plant/thorns lvl 50 dom, ice/fire lvl 40 dom, grav/nrg lvl 41 dom
A grav/kin is my first 50. I always thought of her as a Jedi, better on teams, prone to buffing, more defensive than offensive.
YMMV.
My first 50 and forums namesake is a grav/kin controller. The sets mesh well enough; there's a good, early ST attack chain to take advantage of Siphon Power and, later, Fulcrum Shift.
Siphon Speed helps recycle AoE controls faster, which helps Gravity out a lot.
And although Kinetics isn't known for adding a lot of safety to solo play, Singularity and Wormhole defnitely do.
Grav/kin offers very good single-target damage and (barely) adequate AoE control. Other powersets clearly have bigger and better synergism, but Grav/Kin is decent enough.
maybe gravity isnt for me then, i hate soloing, i love teaming, i love seing those big mobs rdy to be taken out by me lol
@MachineSlave | Infinity Server | Deepdown Traumahounds Supergroup | Co-Founder
Tankers : Ice/Ele, Fire/SS, Fire/DM, Invul/Fire, Ele/Stone Corrupter : Arch/TA
Scrappers : DM/DA, Kat/SR Brutes : Fire/Shield, Ele/Fire(Villian)
Controllers : Fire/Kin, Ele/Rad, Earth/Cold
great combo? im looking for something good for TFs, and stuff
@MachineSlave | Infinity Server | Deepdown Traumahounds Supergroup | Co-Founder
Tankers : Ice/Ele, Fire/SS, Fire/DM, Invul/Fire, Ele/Stone Corrupter : Arch/TA
Scrappers : DM/DA, Kat/SR Brutes : Fire/Shield, Ele/Fire(Villian)
Controllers : Fire/Kin, Ele/Rad, Earth/Cold