For getting around in Delhi, including being met at the airport, you cant beat hiring a car and driver. You can look for recommendations on TripAdvisor's Dehli forums.

Another alternative is Mahavir Yadev and his car from "Rajasthan by Car"..email: mahavir-yad@hotmail.com .. tel: +919810324364.  He'll take you wherever you want to go ... and only where you want to go ... in Delhi or outside. He's knowledgeable, good company, knows Delhi like the back of his hand, will recommend excellent, reasonably priced places to eat and even draw up an itinerary for a trip if you want him to. He negotiates his way through the Hell that is Delhi traffic with great skill and good humour ... and will charge you around £12 per day for his services.