all before i got my kdx 200, i used to ride my friends cr 80 all the time. it was such a thrill sitting on a 2-stroke the first time, letting out the clutch, hearing the ying ying of the engine, and having the front end of the bike in the air as you pull the throttle back. anyway, i was scared **** when another friend of mine got a yz 125. i finally worked up the courage to sit on it and ride it. And i will tell you, it wasnt nearly as scary as i thought it would be. i picked up on it fairly quickly (prior to my kdx 200, with an xr 100 at the tiem) but to tell you the truth, i felt a hell of a lot more comfortable when i got back on my buddies 80, since i could really man handle the thing, and smoked the 125.
so just be sure your ready for a 125 if your going to get one. a lot of these kids where i live get these gigantic 125s at 14-16 and really don't have much fun on them since they try to bring them in tight wooded out trails and such, and get smoked by my kdx and the 80's, and not to mention foul plugs left and right ;)