Respected Dpreview author/reviewer Andy Westlake made the following comments on a dpreview thread several months back in regards to the Olympus Super Fine JPEG setting on the EP-1:
Once you've found where Olympus hid SF compression, I'd strongly advise you take a load of shots at both levels and look at them extremely closely. Then, when you've satisfied yourself there's no visible advantage to using SF, you can set the camera back to Fine and stop wasting your card space.
Seriously, there comes a point where decreasing the JPEG compression level is pointless, it just gives larger files. For example Photoshop allows settings of 1 - 12 for quality, but most experts will tell you there's little point going above 10. Olympus's SF JPEGs are considerably larger than Photoshop's set to 12.
You can read the full thread @ dpreview.com: http://forums.dpreview.com/forums/read.asp?forum=1041&message=33357575