(Based on flight taken between Delhi and Mumbai) - For a LCC, Indigo is probably the most "professional" in outlook. The lady at the check-in counter pronounces english as we know it, has a clean and presentable attire. The Xray machine staff are well. not ill-behaved. The parsers onboard are good at handling passengers who are "not accustomed to aircraft etiquettes". My experience in all this was OK to good. Boarding ceremony as always in India is a scuffle ritual of people who can’t board row-wise or have the courtesy to stand a foot away from you. What disappointed me was that the airline does nothing to have some order prevail during boarding. The buses are best not described, although Indigo ones are still the better of the lot. Food onboard has to be purchased with cash and change is ALWAYS a problem. You will find enough legspace to park your legs if you are 4 feet 10 and no taller. Landing was smooth(maybe an exception). My baggage came out with both zip-locks missing, I lodged a complaint at Mumbai airport. No one has cared to reply to that in 3 months now.
Net-Net:
1) When flying LCC, please check ALL details like flight date, time, route, full and final fare, passenger name and age. You mess up any one and they happily let you know that the money is theirs forever.
2) Book LCC ONLY when you have no hard-stops at your destination. It is an exception when they reach on time. Keep cash handy at the airport to quickly buy eatables when delay is announced, you are left to fend for yourself.
3) Travel light. if you can’t, factor in some money for excess baggage.
4) ALWAYS carry your credit card or enough cash to buy alternate tickets in case you must travel. LCCs take NO responsibility if flight gets cancelled.
5) PLEASE DO NOT use mobile phones while on board and the door is shut. It can cause accidents beyond your imagination.
Hope this helps.