The biggest PITA about mine:
Bolts... I hit em, the heads snap off, then Simon gets the fantastic job of drilling the leftover bits out, and tapping new holes.
Rock washers help, but when I bash the crap out of my skidplates, and make "cereal bowls" out of them (as Simon says, meaning they no longer have nice straight edges, they're now rounded inwards - mainly the skid that replaces the plastic splash guard), the rockwashers don't sit flush, so the edges catch on rocks, and we're back to my original issue.
Another thing to look into, ease of getting to things like the oil filter.