For those of you who have raced this burly bike course in the past, what cassette recommendation might you have for me?
from watching videos
i would say 12-27
and a compact crank
lol
.
I went 12-27 on the back and 52-38 up front (w/ 165mm cranks). I pre-rode the course once (inc. the Wall) with at 39 inner, and that extra tooth definitely helped on race day. There are flats and not-insane downhills where I was glad I had the 52-12 combo.
It depends on your weight and power, of course. I weigh 180 and did it a couple of years ago with a 53/39, 11-32. I was grateful for the pie plate on “the Wall”, but didn’t really need it elsewhere. FWIW, the 32 made it relatively easy to get up the Wall; I just had to watch popping wheelies. 
Bjorn raced it in a 44-25. I strongly recommend against that. Even he says he’ll be bringing different gearing for 2009.
I’d say 39-27 is what most would want. Strong riders are fine with 39-25, weaker probably want compacts. But pretty much, no matter what you have at some point during the race you’ll probably wish you had one more.
There’s an audio clip here http://www.savagemantri.org/Testimonials.html where 2007 winner Chris McDonald discusses his gearing for the race and how his Boulder mates made fun of him for putting on a 27 but that he wished he had a 29.
50/36 and 12-25.
Why not go with a 12-27 over a 12-25? The difference between the two is generally only the last 2 cogs and you shouldn’t really be using those in the big ring so that means they are realy only there for climbing.
In the big ring you will probably use cogs 12-21; which are the same for a 12-25 & 12-27. During the climbs you will have the “extra” gear if needed.
Brian
Whoa…where does one go about getting a 29 or 32?
I was on the phone with my LBS asking the same question yesterday. They thought (for me) compact + 12-27 or 11-28.