Just a few finishing touches, I've been riding the bike quite a bit and it's a ton of fun, and a lot more capable than you would think from looking at it. I've taken it on some of the most technical singletrack and hardest climbs in Marin, and in the rare occasion another MTBer is out there I get some strange looks while mashing away on the drops. To replace the exploding Ultegra derailleur from the last post I went with an XT M770 Rapid Rise, medium cage. Since the pull ratio is the same on these as the road derailleurs the XT 9 speed works perfectly with the 10 speed road shifter/cassette combo. However, the newer Dyna-Sys rear derailleurs will NOT work with 105/Ultegra/Dura Ace shifters, the pull ratio is different. I like the rapid rise, the difference is as you release tension on the cable it shifts towards the larger cogs, so if you are shifting to an easier gear while climbing, or suddenly come from a steep downhill right into a climb, shifting is a lot faster/easier. Makes a lot more sense on a MTB or cross bike to me.
I also swapped out the seatpost for a 0 offset Thomson Masterpiece, the layback post I had put me a bit too far back, especially since I'm used to tri geometry which puts me almost directly above the bottom bracket.
Lastly I switched out the Ultegra 6600 shifters for 105 5700s, they aren't quite as comfy and the shifting doesn't feel quite as nice, but I really wanted under the tape cable routing to keep things out of the way and to prevent anything from getting hung up as I fly through bushes/trees. Of course I won't say the bike is done, but it won't change much from this configuration aside from some cosmetic things. After my next race when I have the time and am not as concerned with the possibility of injury I'll make a video to give you an idea of how it rides. If you like white knuckle, teeth vibrating out of your jaws while going 20mph on singletrack kind of riding I highly recommend a monster cross build of your own, it can handle anything a HT 29er or short travel FS can, just have to be more creative with your lines and have plenty of Motrin and ice waiting at home for after your ride.