Instant Format Cropping In-Camera?

[font color=\'#000000\']Does anybody have any experience with the full-frame Kodak D-SLR's that allow you to change the aspect ratio from standard 2:3 to 4:5 or square? Seems like a fantastic idea; does any masking happen in the viewfinder simultaneously? If not, then are there any real advantages to having the camera do this as opposed to setting up a Photoshop action to do it? I currently manually crop all my digital wedding work to square to match my Hasselblad work; I also crop my actors' headshot work to 8x10, so I leave a little space top-and-bottom on my verticals, but sure would appreciate the ability to mask these formats off in the viewfinder (my 10D doesn't offer interchangeable screens).[/font]