TO answer my own quiestion: YES, even rev 1 works, but you better have some extra heatsinks for the VRMs!
Here are pics of my card after I took the stock cooler off. I decided to use only Zalman ZM-RHS1 heat sinks on the memory and VRMs. The original memory heatsinks were used and I didn't have want to glue them permanently to the board so I just bought 2 packs of ZM-RHS1. If you decide to do the same, make sure you put one of the smaller sinks on the memory closest to the PCI-E connector. The heatpipe of the GPU-cooler is too low for the bigger Zalmans.
Nice pics, tiz always good to see how someone's carried out their work . Those temps look really good for for passive cooling aswell!! Can't answer the the GPU-Z temp question mind... I do have one question, how close is the top of the S1 to the side of your case?
Tried running Furmark and card crashed when GPU temps went to ~72C (took about 3 mins). It seemed that card just turned itself down. So I think the problem lies on the VRMs. I had exactly the same behaviour with my first X1950Pro I tried this exact same Accelero S1 earlier.
Gave up the idea of totally passive cooler on the 4850 and attached one extra Anted 120 Tricool fan on it (sry no pics). After that I had no problems with the Furmark. Ran it for 25 mins and the card stayed stable. The fan was at minimum setting and temps rose to 71C. I thought it was a bit too high, so I cranked up the Fan to midspeed and the temps dropped to ~63C. Temps might have dropped 1C still, but I think that was enough. Antec Tricool Fan can't be heard over the hum of the HDD's in my system.
I hope this gives help to others thinking about this same matter.