I used the Iron Audio Platter for a couple months and very much enjoyed it (also using a Roksan Corus cartridge and a very isolated TT, go to my system on A-Gon to check out what I mean.).
However, I subsequently swapped out the Rega's stock counterweight for the J A Michell Tecno Arm Stub & Counterweight. (FYI - I cannot say enough about this counterweight/armstub and its superb detail retrieval, improvement across all frequencies, better soundstaging, and other improvements. This stainless steel unit is supplied with two weights, one for cartridges of 3 to 6 grams, the other for those 6 to 13 grams. I found installation requires some precision in setting up. It also includes an integral stylus balance: to the rear of the counterweight is an aluminium adjuster with markings at 0.1g intervals.) In this combination, with the rest of my gear, I feel the stock glass platter is a better fit. I must mention that I A/B'd the stock and Iron Audio platters a few times to confirm what I was hearing, yet be advised that what I like may not be what your ears prefer.
FYI - I, and folks on The Vinyl Engine, are looking for someone to scan and forward a copy of each of the P25's manuals (for TT and the RB600). You can reach The Vinyl Engine at
http://www.nakedresource.com/news.shtml, send a message and the files of the scanned manuals to a moderator (try JaS), and help out your fellow audio enthusiasts.