I've somewhat recently started building my own jQuery plugins to modularize some ideas I find myself using frequently. I've noticed many jQuery plugins have a separate
I'd definitely separate any non-trivial amount of CSS from your JS.
Let's go through the pros you have there:
Reduced http requests
If someone uses your plugin they will concat and minfiy all CSS files to one. If not, they're doing it wrong. So still one request for one main CSS file.
Plugin specific CSS isn't loaded if js is disabled
Really? They're already saving the requests for the JS files. I wouldn't care.
Ease of use - can be as easy as one copy-paste and the deed is done.
Well, I guess you can't, physically, disagree with that. But does it really matter? What if your plugin needs images? You can't include them as well.*
*yes, I know about data URI...