I'm joining this late as I am just getting back in town, but I know from experience that PSR not only accepts feedback via the provided contacts, but will amend their reviews if you have info of which they were previously unaware. In my experience PSR has been thankful for the insights and very gracious. I might not always agree with PSR's opinions, as a friend of mine is fond of quoting, if two people are in 100% agreement all the time, one isn't thinking for himself. As others have said numerous times, PSR's contribution to the hobby is immeasurable.
My own theory on the nature of the site is it is a one-man operation. I get the impression he started out reviewing figures he bought but as his site grew in popularity smart manufacturers will send him examples of their output. If they don't they should IMHO - after all, even a bad review still gets their output publicized. And if you aren't confident of the quality of your product maybe you should look for another line of business?