I use an ATEC "Rookie". The design is very sensitive to slight variations in ball size; the less predictable flight path it produces (compared to what comes out of those Jugs machines) forces the batter to be more disciplined and makes the batting practice a little more realistic. Beyond that, I imagine one thing the machines are definitely good for is to emulate perfect risers. The problem is of course those risers stop looking like risers after you've seen three or four of them in a row. So to get the true effect, you'd have to throw a few coach-pitches first to condition the batter; which is a little awkward, and largely destroys the surprise element...