1) Powerful lights make a big difference, both in safety and confidence. I researched my old headlamp quite extensively, the Black Diamond Icon. It got great reviews, but I found it to be not very bright. In spotlight mode, it was way too small of a spot, lighting up maybe 18" wide of trail when pointed on the trail ahead of me, and flood mode was just too dim to be useful for anything but roads. My new headlight, a Petzl Myo XP is awesome, easily 2-3x as bright, lasts many hours (much longer than 1 night), and lights up a good 6' swath of trail brigher than the old 18" spot. It also has a flood setting that casts a lot of light over a large area, great for the gravel road trail sections. My other new light is a Fenix P3D handheld. This thing is insanely bright at a level which lasts 6 hours. Since the headlamp was so bright, I only used the Fenix for the really technical sections (mainly rocky climbs / descents). This was perfect as carrying a handheld all the time can get tiresome. I couldn't be happier with this combo.
2) Carry a backpack or hydration pack with storage on a hundred miler. I typically switch off between my Camelbak M.U.L.E. and my Nathan dual bottle belt in ultras, but since this race was in cooler weather with relatively frequent aid I opted for the bottle belt only. I wished I had the Camelbak during the race as there are many times I wished I had carried more of my own food, and although I got lucky in that I grabbed the right amount of clothes for the evening, I almost didn't and it would be helpful to have carried a lightweight jacket in the backpack.
3) Bring / wear more clothes in colder weather than you're accustomed to. I brought clothes that I typically wear to run in the 20's and 30's, however when I'm training, I bust out the door starting out cold, warm up, and at the end pop back into a warm house. During the 100, I was moving much slower at night than usual and nearly froze. Stopping at aid stations to do maintenance was risky as well because you get cold very fast, it's not like popping into a warm house when you stop running.
4) Adding on to number 2, bring more of my own snacks on the trail. Although the aid stations were well stocked, there were occasions where they didn't have anything out that was too appealing, or times when I was between aid stations and found my stomach growling like crazy. I brought some Shot Bloks for the first time on a race, and they helped a few times (and went down much better than gel), but I didn't have them for the whole race.
5) Bring a full size larger shoes in case needed later in the race. OK, I've heard this one a million times and thought I heeded it, I brought some shoes that are pretty large on me, but by mile 80ish when I put them on, even they were a bit tight. My blister problems went downhill from there, might have been better had I had looser shoes. Looks like I'll have to invest in a pair of "late 100 mile" only shoes. In theory they should last forever if that's the only place I wear them.
6) Come more prepared to deal with blisters. I brought an aid kit I'd put together of various blister remedies, but never having had to deal with them in any serious way in the past most of it was untested. I assumed duct tape would stick no matter what, found out that it comes right off with a little sweat. I picked up some tagaderm that Lynn Saari recommended, saying it should stay on no matter what. I'm still not sure what caused the blister outbreak. I was well hydrated and up on electrolytes at the time as it was late in the night and cool. Might have been the shoe change, but I can't remember if I put the shoes on before or after they popped up. They started as really deep blisters in the ball of my foot so I wonder if it wasn't just internal pounding, they didn't appear to be from any sort of external rubbing. They didn't start till after mile 70 either, I figured if i made it through the day with the heat, sweat, and my 2 pairs of hole ridden shoes that had roughly a beach worth of sand in them half the day that I would be fine for the duration.