It turns out there is a problem in MacOS 10.8.3 using this monitor with the DisplayPort connection - the monitor outputs YPbPr mode instead of RGB and the colors all look washed out and wrong. Looking in the System Information app you can see that the display is being detected as a TV (shows “Television: Yes”).
I then tried connecting using the provided dual link DVI cable, but using Apple’s “Mini DisplayPort to DVI Adaptor” - the colors look correct and “Television: Yes” is not there so this corrects the issue - but of course resolution is limited to 1920x1080 because the adapter is not dual-link. I expect an mDP-dual-link DVI adapter would work fine but those are expensive.
This problem of using YPbPr and detecting the display as a TV when using DisplayPort seems somewhat common and happens with other displays too, I found some threads discussing the issue with other monitors - Dell U2410f and Dell U2713HM.
The fix is to override the EDID returned by the...