For the past month I've been Marksmanship for raiding. I've enjoyed it much more than I did Survival, even though it is currently a bit lackluster DPS wise.
Come 3.1 the Marksmanship tree is getting some love PvE and PvP wise. I believe most Hunters will switch over to Marksmanship for both PvE and PvP to at least try out the spec.
Sometime during the next week I'll post my guide on Marksmanship PvE. The guide will give a rundown on the Glyph DPS, Talent DPS and the rotation a Marksmanship Hunter should use.
I also hope to play Marksmanship in Arena with Double DPS (I currently use Marksmanship for my BG spec, but not Arena spec) come 3.1.
If your bored on your Hunter I suggest speccing into Marksmanship and trying it out for PvE and PvP, I was pleasantly surprised with both. Come 3.1 it will only get better.