Symphony.

Has anyone used JIT in conjunction with any less or sass mixins? Any thoughts to share?

I'm putting a basic set of stuff together for a site build in the future, and I have already got some xsl for outputting retina sized images and paths to be handled by JS with fallbacks for non JS browsing, and it dawned on me that I could write JIT urls into my css, which I use les to compile. I have a mixin for retina images that I was thinking then to update to use JIT.

If I can save some time, has anyone else done it yet?

Nope, but I was planning on writing this, so I am glad I stopped by :)

Actually, when the whole responsive images thing started (about 1.5 years ago I think) the first thing I thought was how JIT in Symphony could be awesomely helpful.

I have not yet done anything with that but would be very interested in trying that out, possibly in combination with e.g. some back-end RESS stuff (there are some extensions being worked on a.t.m. I believe).

I have some cool xsl templates for this stuff. Needs a litle tweaking though to become a utility.

I wrote a RESS-type Symphony extension last year and the first (and only) feature was screen resolution detection. I use it on several personal sites but it didn't generate much interest so I haven't added any features or updated it for 2.3, though I plan to.

I wrote a similar extension to briandrum's (I think I borrowed some of your ideas) that is currently 2.3 ready.

It uses of javascript (jQuery, though it'd be easy to rewrite and bypass jQuery) and cookies to detect and add information for window width, window height, screen width, screen height, pixel density, and screen orientation to the param pool.

Though I use JIT for responsive images, I haven't used JIT with SASS/Compass. I manually resize any media that goes into my stylesheets (since I know the breakpoint sizes, I optimize manually to guarantee quality and save processor time).