Very cool addition to any guitar or bass rig. While it's designed to work with monophonic bass lines, it easily accepts guitar as well. With some tweaking you can get some interesting hybrid sounds, especially when using distortion and additional effects. It definitely takes your library of sounds to a new level of experimentation.
A few of the sounds are useless, such as the "talking" sounds. However, most of them, particularly the sub-bass sine wave and a number of saw waves, are great and can be applied to a number of different types of music. You can also add in a volume pedal to control the intensity of the sound.
This unit is far superior to the Boss SYB-3 pedal, which is very finicky and accepts only perfect single notes. In addition, with the SYB, every time you want to switch sounds, you have fiddle with the array of knobs. The G-5 has a 9-sound memory arranged in 3 banks so that it's much easier to use on gigs.