I speed boost mine, and he's a real rolling stone! 
My earth/kin is pre- inherent fitness, and is my first troller I've ever tried to IO, and I'm trying to piece together a IO set build from the outdated guides in the Guides section.
I'm level 33 right now, so suppose I should just use generic IOs, but I'm also leveling a "ticket" brute, and its seems a waste just to delete all the recipes he's generating at the mid-high 30s that aren't "best sellers."
How are you slotting your Earth/ powers?
Usually if I'm solo and not up to sepnding cash on inventions, I like to focus on Hold, Damage, and Accuracy in Fossilize, and the same goes for Stone Pirson (I usually don't take the AoE immobilize because it neutralizes the wonderful Earthquake ability).
Recharge in everything else usually, with maybe a slow enhancement in quicksand. I like to slot Stoney for Damage and Endurance (a touch of accuracy, since the poor bloke suffers -25% ToHit), and leave the rest to Quicksand.
P.S. Stalagmites and Salt Crystals are pretty sweet, especially the Salt Crystals. Can be a useful tool to prevent said ambush from overwhelming your friends.
Running 33 at the moment, so not much else to say about current slotting other than what I specified.
I use the AOE immobilize + Stalagmites as an AE hold. 
I just don't use it on top of Earthquake. Even with Hasten and Siphon Speed, I'm still wanting more recharge, but when I DO hit both, I find my endurance disappears like rain on hot asphalt.
I have half SOs and half generic IOs at the moment, and one focus is more end redux as I figure how to use these "free" recipes I'm getting on alts (this is my only controller.)
My Earth/storm still remains my favorite run to 50 on a controller although the others are really close.
For me, earth/kin is a natural fit since the earth does the defense debuff which kinetics craves to land the buff/debuff
Triumphant Defenders Forever
Psylenz FF/Psi, ArticQuark Storm/Rad, Symon BarSisyphus Bots/psn, Max VanSydow Thugs/Dk, Cyclone Symon Bots/stm, Blue Loki Ice/Cd, Widow 46526
HelinCarnate:OMG it is so terrible. I have the option to take 3 more powers but no additional slots. Boo F'ing hoo.
I guess I'm in love or something, but Animate Stone practically MADE the set for me solo. My progress went from a crawl to a nice jog. Can't wait to tackle some serious challenges when I hit 35.
That Animated Stone, he's tough and isn't afraid of nothing.
I don't often play controllers, but when I do, I pick Earth Control.
Earth Control, for when you really don't care about slotting for accuracy.
What's that, Mother Mayhem? Can't turn Stoney's brain to liquid? I can't hear you over the sound of stone fists in your face.