Are you building the vivs to go on these? I'd check the dimensions against the vivs you plan to put on them as a lot of vivs are more than 400mm deep, and 800mm wide is less than 3' (which may be a problem if you plan to keep some of the longer species). But 400x800mm doesn't seem a normal viv size to me.
Other than the dimensions, they look like good sturdy shelves. If they were 100mm deeper they'd be ideal for me to shelve our 60cm ExoTerras, I'll be looking for something like this when we move to a bigger house.