Well, only taken a single set of shots, but first impressions:
Wow, ISO 3200, man, does this change your life. The shots are grainy like say an ISO 800 on my Canon Digital Rebel XT EOS-350D, but that is four times less light. Previously my only decent shots were with a 50MM F/1.4 lense shooting at ISO 800 at F/2.0 at 1/250 at EV -1. Now, I can get the same shot with a higher zoom 70-200 F/2.8 (so would need to shoot at ISO 1600 just to get the same quality). But at ISO 3200 and EV -0.5, I can shoot at 1/400 and get most of the shots. Most of the problems are with grain, but it is amazingly good.
The reviews on the web talk about two things: a) there is a bug with black spots near bright white lights which is apparently fixed with firmware 1.07, b) without the 1.6x factor, you need a much dealer wide angle than the 24-104MM F/4 lense that I normally use, so that means another purchase the 16-35MM F/2.8 that is the Pro lense version. 16MM is the equivalent of the low end of the 10-22 EF-S lense that I have for the EOS-350D. But is is bigger and faster.
When shooting basketball in dim courts, some notes:
* Set to AI Servo and just the center aim point, where you point, you focus. Lots of missed shots in a fast game, but better than constanty focusing on the specator near you.
* Anticipate. There is still shutter lag as it takes time spin out, so you have to watch the game, know there is a shot and take it a fraction of a second early.
* Set for Aperture priority at the lowest setting for the lense. F/2.8 for my 70-200. For the 50MM F/1.4, the maximum aperture is so wide that you lose depth of field, so I try to keep at F/2.0
* Center weight the light reading. Sometimes I also use average for the whole shot, but if you set for the default, Evaluative metering, then shutting off all the sensors, causes it to just meter the center. In soccer, I use equal weight the entire image. In basketball, I take it to center weight and then set it to a -1/3EV exposure.
* It likes to take exposures at -1/3EV, otherwise it tends to overexpose
* This should result in shutter speeds in the 1/400 range and 1/250. So you need to watch the motion. 1/500 freezes just about everything.
* Alternatively, you can just manually set everything 1/400 speed and F/2.8 and snap away. Watch the exposure meter so you know where you are. Most basketball games are dark, so you want the camera to underexpose compares to what it thinks is right.