Acid never struck me as something particularly widely used. I was big into electronic music production at the time and I started with Acid + Sound Forge but eventually moved on to Reason and later Ableton + Reason. People who were doing a lot of multitrack editing seemed pretty loyal to Cubase (or Pro Tools if they were using Macs) and then Ableton came along and became extremely popular.

Sound Forge is of course in a class of its own.