I have a 5,480 triangle mesh, I am animating using a action,
it uses 90 ms animation time with the standard solver,
I switch to itasc and it goes down to 3 ms
why would it use so much in standard?
iTaSC is not fundamentaly different than iksolver: like iksolver, it computes the first order kinematics approximation of the armature (the Jacobian matrix), and inverts it to get the bones movements according to least square optimal. Hence, iTaSC and iksolver are not dynamic solvers; they don’t take into account masses, forces and accelerations.
See http://wiki.blender.org/index.php/Dev:Source/GameEngine/RobotIKSolver for more info 
From reading that, it seems speed improvements will only happen in simulation mode. I’ve never had much luck with i-tasc but if you can get it to work it should be much better than standard IK solvers. Maybe your rig has some constraints causing problems with the standard ik solver…
yeah I don’t know what it is, I have 3 chains, 3 bones long, and a copy rot, but it works fine in ITASC