i'm using a Easydive Leo housing and i found it really good. The concept: one housing for different cameras is a reality and also for professional uses (photo and video).
View finder choices: the basic housing leave you the possibility to use the internal viewfinder of the camera. Is not for professional uses but is quite good to frame shots and to make also macros. Videos, with LiveView mode, are really easy to frame.
For sure, during photography sessions, it will be better to use a special viewfinder. For this reason Easydive sells also different products.
1) The Easy Finder: a special view finder to be used inside the housing. This little divice is really important. Magnification i good, about 0,7 x and it very easy to frame images. A good concept leaving photographers free to change type of camera with only a software upgrade.
2) A special optical view finder. A product that will be available very soon. With this viewfinder it will be possible to make fantastics jobs. You will find more info and technical details on Easydive web site soon http://www.easydive.eu.
3) For better magnification, specially for macro, is also available the 45-degree Inon viewfinder. Easydive can sell housings with the Inon viewfinder installed or can install it on old Leo housings.
3 External monitor: a must for the video but i personally prefere the Optcal Viewfinder for photography.
The Easy Finder
The Optical Viewfinder
The Inon 45 degree viewfinder installed on the Leo
Using the default housing, without a special viewfinder, will be very easy to use different types of cameras and models. Same result with the Easy Finder but good magnification and good field of view at a reasonable price.
With a special view finder will be more easy to frame and to work, but it will be necessary to change the position of the viewfinder with different cameras, changing also the back (plexiglass cover) of the housing.
For professional users it will be possible to buy differents back panels with a different plaxiglass to insert the viewfinder.
A great apportunity to use different types of cameras with the same housing, for rookies and also for professional users.
I hope that this informations can be useful.