Thanks for the handy plugin. I was playing around with the new PNG2JPG option in the dev version, which is very useful in specific cases. However, I'd like to not apply that filter on upload. (Otherwise the plugin would have to read users' minds about whether they made a png on purpose, or if they just didn't know any different. :) )
Maybe one way to handle that is if JPG2PNG is checked, then, in the Media browser, the optimize column would offer two options for PNGS: "Optimize PNG" and "Convert PNG->JPG".
It does complicate your currently nice, straightforward plugin, but the lossy possibilities also really change the stakes!
Thanks again for the useful plugin,