Simple List Extensions: Invidious?

The Microsoft Simple List Extensions for RSS + Atom seem like a great idea. You declare attributes for your entries -- like Artist, Date Added, Price, Sales Rank -- and then set the attribute values on each entry. It's a tiny little schema language, with a type system. IE7 can then sort and filter the entries based on those attribute values.

The problem is that once you have that capability, you come to rely on it. If your site has a thousand entries, you can serve it up as a single feed with attributes allowing the client to filter. But you'd organize your site differently if clients didn't have that capability. So, for feed readers not supporting SLE, you'd want to break up your site into several feeds, maybe one for each Artist.

I'm sure every feed reader will have to support these extensions. Otherwise they would appear to suck on feeds that rely on SLE.