This is one concern i had too. Celerio is not Automatic Transmission. it is Automatic Manual Transmission (AMT) I dont have a good idea abt the concept bu what i hear is, Overtaking another vehicle or going uphill is gonna be a problem with AMT. Do u mind explaining this please.
It can handle overtaking just fine. if you put it in manual mode you can change gears whenever you want. but still down shift is automatic. the only problems is when you're in traffic or up hill climbing there's a lot of clutch slip and vibrations. plus the amt unit can't properly maintain a slow speed like a popper autogear box so you have to constantly apply breaks. worst thing is when you apply breaks in slow speeds it automatically presses the clutch. so you are leaping (mostly in traffic).
My friend bought a autogear one and i drove it for a week or so. i never liked that car it seems like i'm never in control. i don't have any thing against indian cars but if you got money for a celerio just buy a Japanese ex: wagon r.
good luck
How amt work is that there's some sort of a robo unit changing gears and applying clutch. its fitted to the top of the gear box.(u can see it working)