IMO coppermine out performs photopost, 4images and all of the rest. We used to have it integrated with our design and vbulletin registration system of our Mustang site, but I took it down since it didn't get used that much.
I do have Coppermine installed on one of my other sites:
http://www.britneyspearsworldwide.co...otos/index.php As you can tell, we completly redesigned the entire structure of our coppermine system. Right now its completely integrated with our design, as soon as we get our forums up, it will be integrated with that as well!
I just like the simple feel and structure better than photopost. Not to mention coppermine has many usefull features that photopost doesny have. Like the ability to send very nice E-Cards via e-mail!