Long (overnight) transit stay is true but it’s the same with any other route.  However, if you take AA or Continental, Delhi is the only stop between US and KTM and because of that you’ll be at KTM within 25-30 hours you leave US.  Also at Delhi airport, you have an option to spent some money and get a business lounge and from my experience it’s worth it.  To my surprise they even have some recline chairs at regular lounge where one can sleep comfortably.  About Delhi airport service, I can't say how was 2-3 years ago but now it has improved a lot.  I like their service better than many Middle East airports like Abu Dhabi or Doha.  Most of the employees at Delhi airport are young around 25 -30 years and they were very professional.  It is going through a big construction so many areas are not yet open and because of that you have limited space to walk but I'll still fly via Delhi again.