I think it looks alright... maybe a little lean.
If you have the money your best route would be have the a/f read on a dyno. Sounds like there are a lot of variables when reading a plug. Did you ride it full throttle and shut down right away? I read you need to do that in order to get a proper reading like scuzz posted. Not too sure though
That plug wont tell you anything, you need to do a plug chop on about 1/4 throttle, 1/2 throttle and WOT. You need to use a new plug for each chop and make sure the quad is all warmed up. Once warmed up install the new plug, go through to 3rd or 4th at 1/4 throttle for about 30 seconds and then pull the clutch and kill it, remove the plug and look at the insulator part only, repeat for 1/2 throttle and WOT. That way you can check most of the curve for correct A/F ratio.