I was running an '00 YZ 250 in the woods, and have NOT liked it too much. Now that I have a WR250F, the YZ sits in the garage.
1) Stiff suspension is gonna kill you in the corners and tight stuff. Forget about it, IMHO
2) Bark busters are a must, I have Acerbis Rally Pro's and love them, they have saved my hands and bars more times than I can tell you.
3) Weight that flywheel. My YZ has more than enough bark to pull the tight uphill stuff, but there are times when I need the extra spin
4) In all seriousness, if you want a woods weapon, MX bikes are not the answer. Once I got my WR250F..... well......