The eBay affiliate program has changed since it first started. A few years ago they'd pay you $25 for every new signup you brought to them who bought something. This was abused a lot, plus eBay reached the conclusion that everybody would end up joining their site and buying something at some point, so there was no need to incentivise sign ups so generously.
The eBay affiliate program then changed to the affiliate being paid on a "per click" basis, calculated from the number of visitors you sent to their site and the listing fees value of the sales made. So the emphasis for the affiliate needed to be a more targetted approach, less clicks/more sales. Because of this model, it became virtually impossible for affiliates to be able to see what had actually sold and made them money. This confusion and obfuscation, along with reduced rewards, caused a lot of ebay affiliates to become disillusioned.
One good thing about the eBay affiliate program is that a click is tracked across all the eBay sites (at the present time). Amazon, by comparison, requires an affiliate to sign up for each individiual country/program.
Whereas 3 years ago it was possible to make a full-time living out of the ebay affiliate program for many people simply "giving it a go", to make a full-time living at it now would require knowledge, effort, stealth, cunning and determination.
Overall: Yes, it is worthwhile being part of the ebay affiliate program when you consider and compare alternatives that might be out there. It is certainly still on my "Top 5 affiliate programs" list.