What I specifically like about Cain is what other hitters are saying about him. He hits low to mid 90's on his fastball, but hitters are always saying it "seems" faster. That "seemingly" faster fastball has been working for two seasons now. I think it's safe to say he's an excellent mainstay for Fantasy stats.
The only downfall that I see for Cain is that whenever he gets rattled, he gets visibly frustrated on the mound and he then walks a guy or two. This is much better than it was last season, but it's still a bit of an issue for him.
However 5 hits given up in his last 29 innings tells me he's worked a hella lot on being more composed out there. Guys just can't hit that rising fastball he throws.
When he's off though, so far this season, he's been able to ratchet it back in and get on track. If he gets through the first 3 innings, he's lights out the rest of the way.