I have traveled with Indigo airline couple of times. I would like to share my experience based on below parameters.
Punctuality: On my 1st trip with them to Delhi, it was bang on time both ways… But on my recent trip to Kerala was disastrous. My onward flight from Pune to Kerala was 2 hours late and worst thing was that we were waiting in the aircraft and in the airport… Our aircraft was waiting for take-off clearance at the end of Taxi-way for almost 45 mins… On my way back from Kochi it was half an hour late… which was acceptable.
Aircraft Condition: I realized that these A320 aircraft are slightly better in terms of legroom compared to other domestic airlines.
Service: Crew was helpful and I had no issues with service.
So, overall it’s a good budget airline in terms of service and quality. Punctuality can be improved, but it does happen sometimes.