MIDI isn't absolutely necessary for the Le Bass, but having the capability is really nice. The MIDI implementation on the Le Bass is a little limited and a bit weird if you're looking to use it to control other MIDI devices, but it works pretty well the other way around. You'll see a pic of my board a few posts back. Using two MIDI cables, I managed to program each of them so that a change on one also engages a change on the other. This is how I use it:
I use Channel A as my clean, uneffected sound, so no matter how deep I might get into effects patches on the H9 I can always call up my regular tone just by hitting Channel A. When I hit the Channel A button it also pulls up a clean patch on the H9 with just a little EQ programmed in.
I can essentially do the same thing using Cold Fusion mode, but it's more of a gritty rock tone. So when I hit Channel A and B together it engages Cold Fusion mode on the Le Bass and also a grittier setting on the H9 with some extra drive and EQ but no effects.
I never use Channel B by itself, so I programmed it to engage the tuner on the H9. It's one button push on the Le Bass instead of two on the H9 to engage the tuner.
On the H9, each patch that I've programmed also either calls up Channel A or Cold Fusion Mode on the Le Bass. So if I'm just running a little Chorus I'll use the cleaner sound of Channel A, but I also have a synth patch that calls up Cold Fusion mode to get a little more grit on that patch. It takes a little extra work to program, but the extra capability makes it worth the effort!