Has anyone tried a chain drive for the y-axis and if so what are your opinions (versus 2 NEMA step drives)?
Chains are meant to operate in one direction which makes them a horrible option for anything precision. I'm assuming that you are talking about linking two separate lead/ball screws. If so, you can use a belt, but you need to make sure it's a heavy enough duty belt to avoid stretch and/or slip for your application.