Bears are essentially tanks.

How is their DPS, compared to Prot Warriors, Prot Pallies or Blood DK's?

4x Blood + 1x Healer, seems essentially the same as 4x Feral Bears + 1x Healer.
A different flavor certainly...

I like that you could run Feral Cats in BG's and Feral Bears in Heroics.
With very similar sets of gearing between the two.
And possibly give them all off-specs too.

I really like Ferals as a team.
But have had more PvP success with the 4x Frost + 1x H.Pally team.
Haven't really done much PvE this expansion yet.