@arihant_enterprises
First of all, allow me to make it clear that I'm speaking as a buyer, not a seller.
As far as my own experience goes, the Speed Post people are very professional and the local staff here are very nice to deal with. For instance, I received an article today and I mentioned to the postman that I forgot to record the delivery times of another two consignments that I received last week. He took my phone number, went back to the P.O. and checked their records. Then he called to tell me the delivery times. Of course, some branches may not provide such friendly services.
They have a detailed tracking system that displays every step of the route: When it's booked at the P.O. branch, when it's moved to a larger branch office, when it's sent to the airport, which flight it's on and the bag number, etc etc until it's finally delivered.
On the negative side, their tracking system occasionally displays the wrong information. Sometimes it shows the wrong P.O. branch of origin, wrong destination and wrong dates. This probably happens when there's a glitch in their network. Even in such cases, delivery and transit times are NOT affected.
It should also be noted that, for security reasons, some P.O. branches do not accept electronic products. Some branches accept them if the package is taken to the P.O. in an open parcel and sealed there under supervision. Some branches don't have any restrictions.
Even in branches where they are more strict, such as Mumbai, Hyderabad, Kolkata, Bangalore, etc., they probably have an arrangement with regular customers because some companies can send me their products by SP. This includes non-eBay sources.
Hope this helps.