Until I stumbled on the following solution I was unable to launch Epson Printer Utility and I could only use the GIMP driver for my SC860. EPU would continually crash or hang if launched and it could never find my printer.

Finally am able to use the Epson driver for my Stylus Color 860 under Tiger. First I removed/reinstalled the Epson drivers from the Tiger disc. This at least allowed Epson Printer Utility to start, but it still couldn't find the printer and would usually hang after that. After some more investigation, I noticed that the Epson drivers that are present in Tiger are not the same set that is present in Panther. The Tiger installer actually removed a number of drivers (I did an upgrade install, so it went and deleted them on it's own). I copied the SC860.plugin file from my 10.3.x system to my 10.4.1 system, restarted, and then set up the printer again using this driver. Now everything works like it used to. This is probably the source of a lot of people's problems. And since you can't get drivers for OS X from Epson for this printer and a number of others, the only place to get them is from Apple.

Also found this page:

http://docs.info.apple.com/article.html?artnum=301175

Looks like Apple chose to replace some nice vendor specific drivers with open source Gimp drivers even though they admit they probably won't work as well. Thanks Apple.