The Canon 5D MkII
Although Vincent didn' t have the chance to test the long-exposure noise performance of the 5d MkII, he did get the chance to shoot some nighttime HD video under ambient street lights, and he posted some frame grabs from the video (here, here and here). Vincent has asked that nobody repost these images due to his agreement with Canon. So, you'll have click over to his blog to see them. And make sure you take the time to read his hands-on evaluation of this beast.
As you look at his shots, keep in mind that these are not 21 megapixel still photographs. These individual frames of HD video.
A Plea for Help: Since some of you will probably get your 5D MkII before I do*, I would be very interested posting any readers' long exposure tests at night. What I'd really to see is comparable frames taken under a clear, starlit sky with 5, 10 and 20-minute exposures at a low ISO. If you'd like to repeat the experiment at a higher ISO for comparative purposes, that would be even better.
* Since I don't have any immediate plans to order one, it goes without saying that some of you will definitely gets your before I do.
Thanks to Joe Reifer for pointing me to Vincent LaForet's blog.