In my experience, the biggest problem with eBay is this:
All your customers, while you might think they are yours and eBay wants you to think that they are yours, but they are actually only eBay customers. They are only loyal to eBay, not to you.
All your hard work at eBay, while getting rewarded, the biggest reward goes to eBay, it builds eBay reputation, not yours. No matter how many feedback you have.
You can NOT build your brand at eBay. Your brand is actually the most important assets of your business in the long run.