Post-possession surprises from Noida Extension builders

Okay I'll be honest — I've been fed up with renting for ages now, and my landlord just raised rent again. I'm finally taking the plunge and trying to make the EMI vs rent math work for a flat in Noida Extension, possibly Sector 150 or 137. I'm looking at projects by Godrej Properties, ATS, and Gaursons. I need some real opinions. How's their actual construction quality after a few years? Also, what about post-possession maintenance charges – are they generally reasonable or do they become a huge burden? Any feedback on their on-time delivery track record would be super helpful. Don't want to get stuck with major delays or unexpected costs.