I am using Hero Honda Street Smart for past 2 years and I am fully satisfied with it.
It has a 100CC engine, same as CD100 model and it is offcourse 4 stroke. The speciality of this model is it has Rotary and Synchormesh Gear. It doesnt have clutch - so you dont have to hold clutch every time you change gear. The advantage is anyone can drive even without having idea of gear. It can start at 4th gear right from standstill.
You will never loose start in road and engine is always ON. You can change gear as you need power and speed balance just as any other bike. While riding hilly road, go down to low gear. Rotary gear is enables you to go to lower or higher one without remembering what was your last gear. i.e gear will move like N->1->2->3->4->N.
Mileage is 70KMPL I am getting in city road after 6 services, initially it was around 45KMPL. Price is just beating - only 35K and it also comes with battery start. The only problem with Hero Honda Street is its look - from front.