A Few Suggestions
This first suggestion is extremely simple. I just downloaded the 5.2 package and unzipped it. I now have 44 files/folders on my desktop. I am glad I keep my desktop clear because for some that could be messy. Could you simply toss everything in a "Photopost Classifieds 5.2" folder? This will keep the folders and files organized for those who have unorganized desktops.
The second suggestion I have pertains to the feedback system. Could there be a couple extra fields? I am specifically looking to have a field that allows feedback to be left for the seller or buyer. It would also be beneficial if there were a URL field that the user had to fill out. This would have to be a link to their ad page. The field should check and see if that url exists (which it must when the feedback is left) and should link to a default "ad expired page" after the ad was either deleted or falls off. It should also ensure that no other feedback is using the same url. this will help prevent people from helping to raise a friends feedback.
It should be an option if we want to allow people to change their feedback. I am personally removing that ability from my site immediately because someone could get in a spat with someone they purchased from and then change their info even if it was a good transaction. Follow-up comments, like with ebays system would be great to replace people changing their opinion.