I currently have a 0/21/30 spec, but I spent my points a little different:
http://www.wowhead.com/talent/?VZqVohxoZGV0iMhhx
I saw 5/5 Efficiency being more important than Impr Concuss so I put the spare one in there.
When it comes to my talents in Surv, they used to be more PvP selfish with Deterrance and CA etc, but seeing as traps are actually used in PvE (Nef phase three Undead Zerg for example) I decided I to spend them there. It worked out nice because I was able to max out three talents.
I lost 2/3 in Surefooted at one point to spend them in Impr FD, but no other hunter in my guild had that so I thought, "What the hell".
I don't know if I will ever do a 31 skill MM spec. I hate the waste of talents. To have to choose 5/5 from:
Imprv Concuss
HM
Imprv Serpent
Imprv Arcane
Imprv Scorpid
seemed slightly daft seeing as 4 of our hunters have 5/5 HM anyway. Just seemed a waste of points. We have enough hunters per raid with TSA to benefit melee dps groups so I am allowed to get away with a 0/21/30.
I did for a short time try this spec, a 5/23/23:
http://www.wowhead.com/talent/?mxZqVohxhZGV0V0Gh
The advantages of that build were getting three talents all at the same time you usually wouldn't be able to get.
3/3 Surefooted
3/3 Killer Instinct
3/3 Barrage
This build relied on me being in a TSA group though, and I missed being "uber" all by myself.
Did some maths (probably slightly inccorect) based on the raw stats Tier three with my other "Wishlist" items and parts of my spec gave me.
Turned out I was able to net 690 unbuffed Agility with 5/5 Lightening Reflexes. Pretty tidy.