AWKWARD ZOMBIE

Actually...it doens't make much diference (At least, not on my computer), it's even better because makes the site faster (It was, in fact, very slow earlier).

You can optimize jpgs? Afaik that only goes for the color palettes of gifs, unless you mean the quality - baseline or progressive scans don't impact the quality.
Comparing some of the png and jpg comics, I haven't really noticed a dramatic difference in size (mostly 50 kb or less difference), but I noticed that the jpgs aren't saved with progressive scans (and thus build up top to bottom instead of going from low-res to hi-res) and the pngs aren't saved interlaced (which would make for a similar effect that lulls the gullible viewers into thinking the image loads faster).