I just did the valve adjustment tonight on my Yager GT 200i.
It took about an hour to gather information (torque values, etc.), tools, lights, rags, etc.
It took about an hour to complete the wrenching part of the job. Would have taken less time but I didn't have a 9mm wrench to tighten the locknut, so I had to tighten the locknut with a socket, test the clearance, loosen the locknut, adjust the center post, tighten the locknut, etc., until I got it just right.
My intake valve was at 0.08mm, so I adjusted it out to 0.10mm. I set it so that the 0.10mm feeler gauge would slide easily in, but the 0.12mm gauge wouldn't.
After adjusting it and buttoning everything back up, I took it out for a hard ride, to see if anything had changed for the worse. It hadn't, still runs great.