Depending on ambient temps I idle anywhere from 22C-33C and at full load up to 68C while gaming/benchmarking my dual 5870s. For example, I was idling at 22C just now, then ran Kombustor and I hit 62C on one GPU. The other was at 56C. The same as I see in games.
Furmark is not the best thing to use. It's not a good real world example. Though I've run it, I don't rely on it's readings for anything anymore. I use the Heaven, and Kombustor benchmarks for a more real world result.
*Waves to Delavan*

(Assuming your the same one from NCIX.)
Hows that AC 5870 Extreme treating you? I had to remove mine for CrossFire.

Otherwise I'd have no sound, and warmer cards. I put that noisy stock fan back on, but thankfully with the second card, I can now RMA this one and still have a computer. Wish it had been a second reference model though.