I am sure people will have negative (and positive) things to say about all couriers, but by and large it appears that Blue Dart/DHL is the most reliable (or should I say "sucks the least") of the lot.
What is the general opinion of experienced sellers?
I am a buyer, not a seller, but after a recent bitter experience with DTDC, I have decided to only buy from sellers who promise to use Blue Dart/DHL for shipping.
(In my DTDC case: I purchased an MP4 player which the seller duly shipped, but the package was not delivered. I had given my office address, and the DTDC folks tampered with the DRS to show that the item was already delivered, and tried to put the blame on my office mailroom clerk. After a lot of arguing, they have now admitted to their mistake, and have agreed to refund the full value of that package.)