I just made a Barbarian, and thanks to two flaws allowed and hero points (which I traded via Antihero for yet another feat) got to start with 4 feats. I took Enforcer and Furious Focus from APG for her, along with Power Attack and Intimidating Prowess from the PRD.
Enforcer's pretty cool, similar to Intimidating Strike. Anytime you hit for nonlethal damage, you get a free action Intimidate check, and if it succeeds, the foe is shaken for 1 round for each point of damage you do. If you crit and demoralize, they're frightened for 1 round before being shaken. Pretty cool in theory, but through 1 session so far, most things seem to have so little hp it's not worth debuffing them because they die in one hit anyway.
Furious Focus lets you ignore the Power Attack penalty on your first attack roll each round. Which is pretty much all your attacks, save AoOs, at level 1. Later on (level 11+), it's required for another APG feat to Intimidate everything within 30 ft anytime you drop someone.
For class features, I think the Elemental Kin one to is probably flat out better than Trap Sense (If a swinging log trap bull rushes me off a cliff by beating my CMD by 1 in the future, maybe I'll feel differently
). Anytime you take (Barb level) elemental damage, you get bonus rage rounds for the day equal to the trapsense bonus.
The others don't impress me too much. The drinking one seems to have some tie-ins with Intimidating, but I refuse to play alcohol-drinking characters, so I didn't even give it a thorough read.
Most of the new Rage powers seem really weaksauce to me, and many of the actual mediocre ones require a higher Barb level and absolutely terrible lower level rage powers selected first. Of note:
Come and Get Me is like the 3E Robilar's Gambit feat, except better because your AoO is resolved
first (so there's a good chance they'll be dead before they can even attack you). Requires level 12, but very nice for a Combat Reflexes Barb.
Flesh Wound is like Defensive roll (even the required level 10+ part), except you can use it once/rage instead of once/day, it's a fort save, you can use it on any attack instead of one that would reduce you to 0 or less (and even if it's from a spell or special ability), you can use it even if unaware of the attack, and not only is the damage halved, it's made nonlethal. What I'm trying to say is, it's just plain better than Rogue's Defensive Roll. Whether it's because this is awesome or Defensive Roll is awful is your call (I vote the latter). ...God defensive roll sucks...
Guarded Life is IMO a complete life-saver and well worth taking eventually. Turns damage that would kill you into nonlethal and auto-stabilizes you.
Ground Breaker is just plain cool and gives a Barb a weak battlefield control ability. I could see this being awesome in a confined area. You smash the floor and turn your square and all the ones around it into difficult terrain that you ignore. Bye bye, 5 ft steps! Can also knock people prone. Badass.
Knockdown is like Knockback, except you can trip a fool.
Reckless Abandon lets you trade AC for attack bonus. Combined with Power Attack, it's basically a poor man's Shock Trooper.
Smasher: Once you have enough rage rounds to blow a few smashing important objects open, this is ok. Not high priority, more for when you run out of good rage powers for the required level you can meet.
Spirit Totem (and Lesser and Greater ST) is one of the few rage power trees I really like. Each gives something new and useful. Lesser gives a weak bonus attack on anything near you each round. I prefer it to gaining a natural weapon for the versatility of when in my attack order I can use it. ST gives an extremely useful Blur effect against anything not melee attacking you from an adjacent square. Greater makes the free attack better.
Witch Hunter: If you're getting Superstition, may as well get this.
