Say you're using chorus and reverb for part of a song, but you're using a compressor, EQ, and maybe a preamp for the entire song. You can program one switch to turn both effects or any combo of the items on and off with one touch. Or maybe you want to use the volume pedal as a volume for part of a song, and to change an effect parameter, like delay time, modulation rate, etc... for another. It's possible with Tone Studio.
My live board also includes an external tuner/buffer/mute, compressor, a Q-strip EQ / DI, and distortion. My main use for the GT-1B is for sounds that don't get used continuously, like chorus, phase, flange, octaver, t-wah, volume pedal, and slow gear. The Boss effects are good enough for live use to get the job done and leave many pounds of individual pedals at home. I have a series of presets that are simply one effect that I can call up on demand and operate it as a stand alone pedal, ex:// a phaser or chorus, assigning knobs and switches to act like the pedal in that preset. I also have an "all off, pass-thru" preset in the first slot. The "all off" preset can be handy to copy at different areas so you can pop back and forth between a complicated preset or two and a straight & clean bass signal.
I have several nice amps, including a Mesa TT-800 and Little Mark III, so I typically only use the Boss preamps when I want a distinctively different sound during a show, or while practicing with headphones. I have a few crazy presets, like Slow Gear "bowed" swells, a fake stand-up acoustic bass sound that's surprisingly good, and even an organ sound I can use to do baseball and hockey sound bites in sports bar. The fake stand-up gets a lot of compliments when used on rockabilly, oldies, or mellow country stuff.
The unit is also a nice battery powered headphone amp, complete with aux in. I use it all the time when my wife is asleep.
The hard part when I first got it was not going down a rabbit hole and staying up all night playing with the device and Tone Studio.
