At that point I plan to submit a patch to ImageMagick to detect it and enable the user options if mozjpeg is being used. I believe downstream support in libraries like ImageMagick is key to adoption, rather than adding makeup to a pig (input support for N formats in cjpeg).
I am also not convinced by Trellis yet. In my tests, it introduced a faint blur. In fairness though, I only tried 4:4:4 and not 4:2:0 as Mozilla apparently does. In the latter case, additional blur may not be noticeable.
As for trellis, you should play with the different metrics available (MS-SSIM etc), but I agree I have not been wowed yet.
This isn't exactly new ground beign covered here, nor is it tied to one image format, so I wish people would be a little less NIH-y sometimes...
Because we haven't been able to solve that problem yet, we use JPEGmini, a proprietary (but not that expensive) vendor solution.
I'd also be really interested in an ASM compiled version that's easy to use from node (and possibly the browser).
* jpegcrush/jpegrescan trick: tweaks details of progressive JPEG for maximum compression (each scan gets its own Huffman table, and JPEG can arbitrarily divide data into scans). That's 5%-10% improvement over jpegoptim.
* if you're creating a new JPEG or lowering quality of an existing one, then it uses trellis quantization. In the lossy compression step instead of naively throwing away data, it evaluates lots of combinations to find best bang-for-the-buck combination. That's an extra 5% improvement in quality/filesize ratio.
libjpeg-turbo and IJG JPEG libraries also have "cjpeg" tools as their basic command-line encoder. The tool for mozjpeg works almost exactly the same way, but it has some extra option flags, can take JPEG input (the others can't), and re-defines the "-baseline" option to something more intuitive (see v2.1 release notes).
(and FYI, most sites that optimize their images (e.g. Facebook) use progressive jpegs for efficiency).
To that end I plan to add support to ImageMagick, and perhaps write a PS plugin.
I'm not really sure why you think that this stuff is meant for designers. Recompressing images is a frontend optimization. It's something you automate. It's a task for machines, not humans.