Once I went to this airport as it was nearest to the beautiful city of gangtok. the airport was basically an extension of airforce base. the size of the airport was not that big as of other domestic airports but it was safe for the planes to land in short span of time.
The numbers of runway too is small and probably there are hardly 2 runways on that airport. the frequency of the flights from the airport too is quite low and only a few flights are available for prominent cities of india. you can easily get a flight for delhi from bagdogra.
The security of the airport is quite good inspite of the fact that it do not have large amount of crowd. if you ever got to gangtok for visiting that beautiful place try to reach via air so that you can enjoy the beauty of that tiny airport. hope this review helps.