Well, that is most certainly a soloing build. Not something I would use for Arenas, BGs or groups. As I said in an earlier thread, you have to make a decision. Do you want to go as pure DPS, or Utility? For PvP, you ought to consider Utility as well (CC and Survivability) as DPS. You need
both.
I suppose for 2vs2 Arenas, your build has some merits, but it quite simply doesn't have anywhere near the burst or staying DPS needed in bigger clashes like BGs or 5vs5 arenas.
Granted, you have Intimidate and Traps. But you have nothing resembling real damage talents besides your pet. And you simply can't completely rely on him. Anyway, you want a jack of all trades Character. A Hunter that can do DPS, CC, PvP and Survive nigh everything. It's cool, Hunters
can do all those things. But not all that well.
If your focus is mainly on PvE (Heroics, perhaps Karazhan) with PvP in between, your build should reflect that. If you mainly PvP, your build should reflect that, with a couple of PvE talents thrown in to boot.
Well, if you have the Agility to pull it off,
0/21/40 isn't all that bad for a combined PvE/PvP specc. It gives you Scatter, Wyvern and lower Trap Cooldowns for survivability as well as the Deterrence "Oh Shi-!" button when all else fails. And everything on the way up to Scatter gives your crits some fairly ugly damage, even though you won't have the sheer BM dps in a raid. Not to mention that in PvE, this build is off the hook, literally. Your CC is enormous while allowing for good (not great) dps in instances.
41/20/0 will lose you alot of CC and "Oh Shi-!" measures, but will increase the sheer DPS you are pumping out. The effect of Lethal Shots and Mortal Shots is quite simply impossible to understate. The major problem with going BM, is that going less than 41 up the tree will lose out on the single best talent a BM can have for PvP, thus you
have to lose Scatter Shot. Wouldn't recommend it for PvP as such, since it doesn't really have the survivability of other speccs.
I honestly don't know much about Marksman PvP anymore. Pre-TBC I PvPed with Marksman talents to quickly pound down an enemy. You are going to have to ask a Marksman about it, but I would hazard a guess and say
7/41/12 would give you good burst damage, one "Oh Shi-!" button, and in general very high burst damage. I wouldn't venture into a Heroic or Karazhan with this though, unless I had a crapton of mana potions, and an understanding guild.
It all boils down to this: You can't have one build that does everything well. If you want to do something, you have to specc for it or quite simply come off as less than average in that particular venture.