Hailing more from the financially destitute camp than the "I have 3 pit bikes and 8 sets of carbon wheels" camp, one of my friends has taken pity on me and given me a great deal on a slightly used set of Challenge Fango clinchers and a brand spanking new set of XTR mtb pedals.
Here's my impressions:
Oh my, my... Let me just start by saying, my old pedals were these old, gold Ritchey SPDs from 1996. If I dismounted in anything but dry sand and/or dry grass, I could pretty much guarantee that I would be riding unclipped the remainder of the race. These pedals just wouldn't engage unless it was a squeaky clean cleat/pedal interface. Not so with the XTR's. These have plenty of room to spare for things like mud or snow. And with those big, menacing clamps (the left one took a pretty nice "bite" of my calf on a botched dismount) when the cleat is pressed on them, they just open up and latch on. Done.
Challenge Fango Clinchers
I was running a set of Michelin Mud tires prior. The Muds are nothing to scoff at and they are an excellent tire, but I was really interested in trying something a bit more supple. Now, I don't have much to base my comparison on, nut these are the best cornering tire I have ever ridden. I'm not the best bike handler out there, but these things made me feel like I could corner twice as fast as on my Michelins. I was running them about 30 psi and they felt plenty supple and absorbed the bumps well enough to allow for steady powering. I guess the truth is in the races...
On other thing I "upgraded" - my seatpost. The bike came with some cheapo carbon post and the clamp broke. So I took my Thompson off my old road bike. The Thompson has no set back so my position is a bit different, but I'll live with it since it was free.