I too think the answer to success in RSS is the sponsor providing as much raw data as possible and the affiliate learning how to manipulate it, especially the description. This will ensure your output is truly unique and not just because you have a different size pic than the next guy.
For the webmaster not skilled in this manipulation, anything less than customization options from the sponsor to the point that each affiliate gets his own feed with unique text will tend to suck in the long term unless you are the only webmaster pushing that feed.
Most Sponsors who have jumped on the "yeah we have that RSS thing too" bandwagon in the last year remind me of a couple of television commercials.
The first one for fandango, where you can buy your movie tickets online. The guy that doesn't know what the fuck fandango is overhears the couple mention it at the ticket counter and thinks all he needs to do is mention that word and he will be cool and get his tickets.
The other one is the latest verizon commercial, where the guy asks the verizon competitor if their network can do that an he says something like "sure why not" without understanding what the guy wants.
It's weird that there have been so many threads about Sponsors asking affiliates what they want in a feed, usually after Affiliates complain about what they first put out, that you would think the latest sponsors coming out with RSS would have some pretty hot feeds, but no.
In a nutshell, for a Sponsor to really stand out, they need to do two things that are of course easier said than done.
1) Have as many customization options as possible, ideally including a text generator to pump out a unique description for each affiliate's feed so the lazy/busy webmaster can grab it and go.
and/or
2) Provide as much raw data as possible so that the affiliate can take customization to the next level beyond whatever can be generated by the options offered by the sponsor.