Split the topic so this discussion isn't diluted with the silly tape vs media nonsense.
The EX3 is going for $8320 pre-order price at many online stores. The EX1 at $6499 (with a 8GB card rebate in the US).
The Letus and other 35mm devices allow the user to use shallow DOF. That is something that isn't always desirable on natural history shooting. Plus the overall sensor crop factor makes even the shortest lenses a longer lens. That's why there are 6mm lenses for 2/3 sensors.
One of the reasons why many productions have moved to a CCD camera for topside shooting is due to the jiggly running and stuff (see Ultimate Survival etc) which can stress a rolling shutter response on a CMOS sensor. So know what you are shooting and plan for it.
The Flash and Nano modules from Convergent may give you 4:2:2 MPEG2 but that doesn't guarantee the Beeb will accept it for principal capture. They have a rather funky stringent list of criteria for HD capture and have excluded even S16mm film, which has more than enough resolution with the right telecine. That'd be grasping at straws until they finally announce their ruling.