Thanks for a great plug-in!
I've tried to style the contents using CSS and I've bumped into a couple of issues.
First the whole "plug-in area" could need an enclosing div with a unique class (e.g. "sp-feeds").
This should preferably not be an identifier since that makes designing all usages of the plug-in hard. (I guess a compromise could be a class and an id).
This makes it easier to limit CSS to just the content from the plug-in.
Then each feed could use an enclosing div with a unique class (e.g. "sp-feed").
This makes it easier to design the display of each feed. The same discussion for class vs id as above can be applied here.
Each article in a feed could use a class (e.g. "sp-feed-article") to make it possible to design all the articles with one CSS entry, instead of having to design each unique article by it's id.
Finally the powered by and stats text at the bottom could need an enclosing div (e.g. "sp-footer"), in order to design them separately.
Here's an example of why I'd love to have the above divs:
I had a design where I made things "float:left".
I had to add an enclosing div around the short code for the plug-in (which is a bit impractical). This in order to limit my CSS to just the output of the plug-in.
I still had the problem that the "powered by" and stats ended up at the top of the list of articles at the far left.
There is, given the current HTML of the plug-in, no way to place this text at a more appropriate location since I can't address it with a CSS command without an enclosing div with a class (or id or both).
I hope this rather long entry is of help.
Thanks again for a great plug-in!