I have to say that having now played quite a lot of Feral PvP in the beta now, the spec is stronger than I first thought. I haven't really noticed the loss of Barkskin, the double SI charge seems more than sufficient. Due to the changes in dmg/HP ratio you don't seem to get quite so annihilated during stunlocks. That being said I do worry that could become a problem as damage starts to scale...
The feral self-healing seems pretty insane though. With Ysera's gift, passive 20% increase in healing, HT on PS procs, keeping rejuv up at all times in cat form, I find I can mitigate a lot of damage through healing. Also Glyph of Nine Lives is a must for PvP.
The main issue I have at the moment is recovering from those 'oh shit' burst moments. If you know its coming SI is fantastic (your Chaos Bolt tickles me lolz), but when you are already behind missing Might of Ursoc hurts. I think we will have a slight change of play-style, more like strike, kite for a bit, strike, kite for a bit etc.
As a general comment in small scale pvp melee (including feral) feels very strong versus casters, though healers are still pretty hard to burst down when played well. Melee vs melee seems ok, save the current tuning issues with the likes of warrior!
In large scale pvp like Ashran, being melee is kinda pointless. All I could do is stand back and lazor kitty (for not a lot of damage!). If you even attempt to get close to the fight you get insta-gibbed or just die from the mass AOE spam.