Darin's description of P1 of Thin Air is very accurate - the crux is the first 25 feet of thin face climbing with microcams and small nuts in the thin crack for pro. The intimidating-looking roof is actually fairly easy to pull (on its left side) with the great hand jams and jugs directly above it. Fun (and easier) climbing ensues above the roof. Pitch ends on a large ledge with boulders (double bolts). Note that there are now 2 more pitches (sport) that have been added to Thin Air which take you to the summit of the formation (Watts' book mentions only one, runout 5.9 pitch).
Pitch 2: 5.8 - 5.10a, bolts. The pitch opens up with the crux boulder move. It's highly reach-dependent. Ryan Lawson's book (see main page) rates this pitch at 10a. That's probably an overestimate. If you're somewhat tall (or skilled), this should not feel harder than a 5.8. Belay on a small ledge with two new bolts.
Pitch 3: 5.10a, bolts. The opening move of this pitch is the crux of the route. You need to pull a short but steep bulge. Look for a three finger pocket left of and above double bolt anchor. Once past this move, climbing eases to a 5.7 face. Belay 30 feet below the summit from two bolts (nice big ledge).
Either rap the route (rap back down to top of P2, probably single rope; then rap left off a set of bolts on top of some sport route, again probably single rope) or (better) scramble (class 3-4) to the summit of Koala, downclimb to a sandy "alcove" and look for rap bolts atop a "hump" in the rear of Koala Rock. Single rope brings you to the ground.