IMHO, shifter feats aren't that awesome, simply because you could get much better things for the measly 8 feats you get w/ barbarian. But, if you are like me, and like shifter fluff, you will do it anyway XD
In that case, you will burn almost half of your resources easily, for getting that 2nd shifter trait is a good thing. For one XXX Elite feats seem a nice choice.
Now on traits. Beasthide is nice for barbarians. +2 Nat AC (4if you take elite feat) offsets the AC loss while raging, and +2 CON is one more round raging AND +1 hp per level. Gorebrute is awesome if you plan on making a charger build (not if you have pounce ability, though). Longstride provides +1 AC and 10 more ft of speed (20 if you take elite feat). Longtooth gives you +2 STR and additional attack (is better than razorclaw, cos you will be most likely wielding a two hander). Wildhunt gives you scent and CON, which are nice but not all that awesome.
I would probably take longstrider with elite feat (for 20ft speed increase) and either beasthide or loongtooth.
As for feats, if you take longstride, take elite. As second shifter feat go for reactive shifting or shifter savagery if you gain natural weapons.