The cleaning is the biggest thing. I've seen this in a few places and there are always red and blue tints left over from erasing. Old writing tends to be a bit hard to take off without some kind of liquid spray.
We've painted a whiteboard-sized area of our office with this stuff. There's no border to tell you where the whiteboard paint finishes. As you'd expect, the ink is no longer confined to the bit that's wipe-clean. Otherwise (with the spray proviso above) it's been very useful, and we can always extend it with another pot later.
Another alternative is those statically charged pieces of "whiteboard paper" - Whiteyboard is mentioned below, and there's also http://www.magicwhiteboard.co.uk/ - although they don't stay up tidily for much longer than a couple of weeks. I think they're only really meant to last e.g. a day-long meeting.