VERY important in so many ways. Assuming you are asking from the standpoint of coaching a HS team - it allows multiple hitting stations, maximizes cuts in a short period of time, frees up the field for defensive and other drills/stations to be run simultaneously, allows the players to toss to themselves, gives an opportunity to work on mechanics with tee and front toss stations, allows for multiple-cut sessions with just a few players without having to shag, and on and on. A two-tunnel set up is far better than just one and not much more of an expense if you have the space. Be sure to give plenty of width. If you have a program parent or supporter who is a welder or in construction, you can save a bundle.