Ebay.in has changed a lot since it came into existence. Previously it was a no good site but now things have changed a lot and sellers are really aware that their rating will be directly proportionate to their sales.
Most of my purchases on Ebay were really clean and I did not face any problem with the products, however there were few transactions wherein the quality of the product was really bad. My words of wisdom:
1) Only buy from sellers who have been there long enough(check the join date).
2) Only buy from sellers who have 98- 100% satisfaction rating.
3) Read the feedback of their previous customers before buying to understand whats good and what went wrong.
4) Read the product description thoroughly to see if they have mentioned something about the product being a "like original" or so.
5) I always prefer Credit card transaction only as they are simpler to be refunded.
The bottom line is if you research well, ebay is a good site to get awesome goods at decent prices.