If you're talking about consistency, I'm not sure why you'll pick Production IG. They have their fair share of duds too.
That's true, but recently I think their TV work has been fairly strong, with Kimi ni Todoke s2, Bunny Drop, Blood-C, Guilty Crown, their Young Animators shorts, and the upcoming Robotics;Notes.
Oh, and apparently the official English title for Wasurenagumo is Li'l Spider Girl, heh.
Edit: BONES, Ufotable, and A-1 Pictures are also studios which would easily be notable for having solid backgrounds in most of their shows as well.
Eh, based on what Jexhius has been posting from Eureka Seven Ao, I don't think I could in good conscience list them there. Ufotable did good work in Fate/Zero, but I want to see more. A-1 Pictures is another one, sure.