Hi mmphadke,
You have rightly stated, you should leave positive feedback only after you are completely satisfied by your transaction experience.
The practise of asking for early feedback in exchange of free gift is considered feedback extortion, and is discouraged by eBay. I will encourage you to report the same to eBay, so that the seller can be appropriately educated.
You may report the same by following:
http://pages.ebay.in/help/contact_us/_base/index.html
Problem with Other Members
Feedback Concerns
User threatened to leave feedback by extortion
Thanks and Regards,
Sapana