I have 25 hours on my 350 XC-fW and had yet to have any kind of problem. Valves are in good nick and oil has been coming out clean. No flame-outs or any other weirdness. The bikes are a little hard to start cold. Of course if you use the "choke" they fire right up.
I picked up a second bike for this years Baja 500 and have been prepping it with mostly the same parts as my personal bike.
I installed HDB stuff on both bike, of course.
On the first bike I used the Unabiker rad guards but decided to go with the Bulletproof on the race bike. Much easier to install and alot beefier. They cost almost double but after 1 crash destroyed a radiator and the Unabiker guard I was wishing I had spent the extra money on the BP stuff.
Took it out to the desert this weekend to set up the suspension and ergs.
And finally added the all important decals!
I leave Friday, I hope I remembered everything....