There are many issues:
1. Running just 5 trains in 24 hours
2. Trains with no punctuality
3. Takes upto 2 hours for a 30-35 kms journey.
4. No dedicated platforms at major stations...
more...
5. Overall it gives a feeling of half hearted attempt
Crores of rupees are going to be spent for laying new metro line to airport causing huge inconvenience during next 8 years, but 3-4 km link line on broad gauge cannot be laid upto airport!!
Expecting a savings of 200 rupees, you will miss flights if you depend on this arrangement. On return journey also, even if you opt for train, you will spend 3 hours to reach your destination in city.
Dedicated platform at YPR and BNC with punctual hourly service round the clock only will help.
Airport train should get preference over any other train as other trains can make up the lost time in their overall journey, but airport train cannot make up any lost time.