It was the first ‘machine’ I bought for my studio in 2002, and I still use it regularly. The appeal to me as a trainer is:
1. You can vary the resistance from almost nothing to a lot which makes it very useable to all fitness levels.
2. The resistance is not linear, meaning that it starts off much lighter than it is in the end range. This can be of advantage for upper body exercises when the shoulder, ie. the rotator cuff, must not be challenged.
3. If you want people to learn to do exercises at a gym, the Bowflex is close enough to a gym environment to help make this transition easier for clients.
4. It is extremely versatile and perfect for one person who does not have a lot of space and wants a lot of function from one machine. There is really no exercise that you cannot do on it.
5. Particularly for the upper body exercises, it does not mandate a particular path of movement which makes it really more like free weights (or maybe Freemotion machines) than regular machines.
6. It is virtually maintenance-free. In all my years of use, it may have needed the occasional tightening of a screw but nothing of any consequence.