Hi,
For the studio I absolulty love the Leaf backs.
As long as you can stay within ISO100/200 or lower I think they are hard to beat for skin tones.
But make sure for conversion to TIFF16bits use the Leaf software for best results, I don't really like what ACR is doing with the files.
If you want to shoot higher I would advise the Canon 5DMKII, I'm using that one as backup or for those situations where I need a DSLR.
The tethered software is very good, and very stable, plus you can show the shots on your iPhone or iPod touch while shooting.
Hope this helps a bit.