Half way through the game on Super Soldier and finding it's not much of a challenge.
The early stages were tricky while getting used to the mechanics until I realised you can simply stealth and walk past 90% of the battles. By the time you're forced to fight some Cell you have a sniper rifle, and can pretty much clear most levels with it from the starting point, especially with the large amounts of ammo around.
When the Ceph turned up it got even easier thanks to the silenced shotgun I found. I simply bought Covert Ops (no footstep noise) and nailed every single one in 2-3 shots, with the others hardly noticing.
I am enjoying it, but hope it gets a little tougher.