Yup. It's always on. I started using it with my bass rig ... and I don't use effects on bass ... then moved it to my guitar board. I may get another one for bass eventually. It just fattens the sound and you control the fat. Right now, I'm playing a PRS Hollowbody Spruce with piezo and the piezo has seemed to lack guts in the bass area. The BBE has been an important part of the fix for that. Now the PRS piezo, although it does not sound like a Martin J-40, does have some low-end punch. Woo Hoo!
Yes, for the price it really is a neat unit. I wouldn't want to pay much more for it though. The lo contour is somewhat like a resonance control, and the process acts somewhat like a presence control (although I think it boosts around 2khz). It does at a sense of tightness to your sound, almost like compression, but of course not exactly like it. You just have to try it yourself and see if you like it.