I've been thinking on this as we are getting to that point where room equipment needs refreshing and discussed with a couple of teachers and the biggest concern that has been voiced is that the screen will not be big enough. We have 70"+ IWBs at the moment, at 4:3. 50" screen would be widescreen so at a random poll of the internet I come up with dimensions of 120.52x72.42, giving an area of 87242cm^2. Currently our dimensions of our smallest board are 109.5x146 giving an area of 15987cm^2. That is a fair amount of lost space. The teachers I spoke to said that the screen would be too small unless they all gathered around the front.
One of the teachers I clued into this and wanted an opinion from hates his whiteboard but he said the whiteboard would win over this as the whiteboard you can at least "write" on it or annotate something being shown. With a TV screen you would loose that area unless you start faffing with typing or launching a program to use as a whiteboard (think Fraiser uses Penultimate to simulate a board) & then you loose your features such being able to annotate web pages or random apps.
No one seems to use the point that is really pushed for IWBs, to save a whole board of annotations for a later, but do use bringing up a file and annotating it.
The IT teacher I spoke to said that they do use the interactive part of the board to present from the front & to get kids up to show but with a "device" that could suffice.
So my conclusions are that the boards could go if the interactive feature could be replicated (tablet with RDP/VNC, remote mouse, remote wacom tablet,etc). A DECENT projector is what is really needed. My thought on replicating this & spending less. Dump the IWB, keep the projector (if it is a decent one) but paint the surface to project on with whiteboard paint. Not sure how glossy or reflective it is but this would add some interactivity to the setup. Create a diagram on the computer and it can be annotated on the "whiteboard" wall, or have a blank table that can be filled in. Use a big enough bit of wall and you can have your objectives, date & overarching question permanently displayed in one corner without taking up screen space or going missing when swapping documents.
His is a nice setup & looks perfect for his teaching space and style but I can't see it working wholesale, even ignoring the whole Apple centric view of it. But he does have a point about boards.