While doing the Markleeville "Death Ride" I hit a pot hole going downhill and got a pinch flat on the front tire. After fixing the flat I finished the ride (descended Ebbett's and rode up and down Carson Pass). At home I noticed a hole in the tire, and while replacing it noticed a small dent in the wheel rim (presumably from the above incident). I mounted a new tire and have been riding it, but I'm wondering if I should replace the rim even though it's still functional. Any opinions about how significant a dent needs to be before replacing? Does the fact that it still holds the tire on fast, steep descents make a difference?

Rims can get dented in several ways. One is where the rim sidewall is flared either in or out, another is when the rim as a whole is pushed towards the hub, causing a flat spot.
For a rim braked wheel, if the dent isn't serious enough to upset the braking, I'd leave it alone. For a hub braked wheel I'd have to look at how sharp/deep the dent is. Any sharp crease in the rim and I'd scrap it. A smooth bend I'd probably try to straighten it for reuse if it's less than 4 mm.

A few considerations. Dies the dent widen the rim a bit causing the brakes to pulse or grab? Is it deep enough to affect tire mounting? Is it deep enough that you can feel it when riding?

Deep enough to fee riding or affect tire mounting might be cause for replacement, though sometimes that can be aligned out, but if it affects braking that needs to be dealt with.

Unless you have hard anodized rims a slight wide spot can be pushed back in with a pair of Channellock pliers. Use a cone wrench or something to spread the load on the good side, and gently squeeze the blip back into line. Work by degrees and check by spinning the wheel while holding one brake shoe in to just make contact. Then repeat the process on the other side. You don't have to get it 100% perfect, brake shoe wear will finish the job for you.

Hard anodized rims cannot be salvaged this way because they're brittle and will crack.

Usually ther's no need to replace the rim, but check the area for loose spokes, and if necessary bring it to a good wheel man for realignment and retensioning.

+1. Excellent response form FBinNY!

The rim sidewall is flared slightly in and does not affect braking, at least I cannot feel it in any way. The wheel is still true and none of the spokes have loosened (Mavic Ksyrium Elites). I'm going to keep riding it and keep an eye on things (until my confidence in the wheel is back up). Thanks for the responses.