Hi,
Bajaj has come with Pulsar DTSi, one of the best bikes in its cadre.....but KB125 was one of the best it had put forward a long time ago. I own a KB125 for the past 9 years. I still use it and I can claim it be one of the best. In terms of power, it may not match a Yamaha 100. But lot of good things have are there compared to a Yamaha.
Good things:
Maintanence is low and very cheap. How rugged or roughly you use the bike, go to the nearest workshop, spend 800 Rs MAX, your bike becomes new again.
Good mileage.
Good stability in riding (Except speed turns in Steep roads, the front side becomes a bit unstable).
Good seating (Two fat and huge people can comfortably sit in a KB125). You have to compromise for that on a Yamaha.
Good for long drives.
Good for city driving (Handling traffic is really easy).
Bad things:
Suspension wears of easily. But again its cheap to maintain.
Shortage in genuine Bajaj spare parts.
Nothing less... nothing more....KB125 is the BEST...