Whether you are a musician or not, all creative and technically-inclined people should be excited about the Monome interface:
CDM links to a early adopter's impressions, which are highly favorable.
Now, I know what you might be thinking: it's a box with buttons and lights. Is that supposed to be cool? YES. It is very cool, because the Monome doesn't impose any restraints whatsoever on what you do with those buttons and lights. They're completely software-controlled, so the display is independent from the input functions. And unlike the Lemur touch control, which fits much the same niche, the Monome has the tactility of physical buttons.
You can build a Tenori with this. You can make a drum machine, complete with display. You can use it as a sample trigger. You can assign synth tones to the keys and play it like a very funky keyboard. It could be used to control and display an EQ. And these are just the musical uses. It's also a very small Game of Life board. With simple software to interface between midi and keystrokes, it can be a macro keyboard. It could be an image password. There is so much cool stuff you could do with one of these.