I would like some kind of protection for my 06 DRZ 400, I do mostly back roads and single track with some tight technical stuff in S. Utah and New Mexico. The seat height of 37 inches and not always being able to reach the ground (I'm 5'11") causes me to dump the bike usually at really slow speeds (it is geared down) once in a while. The plastic fairing over the radiator is taking a beating and some of the fins in the radiator are getting compressed (no leaks...YET). I put on radiator guards but they are aluminum and don't add much side impact protection. I would buy any kind of crash guard for the radiators, if they existed.
I have compared my geard down DRZ 400S with my brother's stock CRF 230 on many very challenging trails (sand, rock, slick rock and hill climbing, 4000 to 9000ft elevations) in southern Utah. The 230 requirs a lot more shifting but can easily keep up with the 400 for equally experienced riders in most situations. The 230 actually outperforms the 400 in tight techinal sections because it has a much lower seat and center of gravity. Dump the 400 with the wheels uphill and it takes two to get it back up. The virsitility of the dual purpose set up means when the trail turns to highway we just keep going. We both added skid plates.