Do you find distance learning to be effective?

Yes, it is. There may be fields and specialties that are not available nearby.  In this case distance learning is a solution. You can say it as fair not far.

It is quite effective if: A) The Trainer is Good, B) The E-Learning platform is robust and has a great technological run, C) The Trainees are geographically spread over

YES, IT IS VERY EFFECTIVE MOST OF THE TIME