Ease of installation: 8/10: relatively straightforward, but some soldering required. 2 batteries demand more space.
Ease of use: 8/10: boost-only not quite as intuitive as the popular boost/cut setup.
Noise: 10/10: very quiet. The treble boost is even quiet at moderate settings.
Headroom: 10/10: tons of headroom. 18 volts really seems to help.
Tone: 10/10: A wonderfully musical circuit. It's hard to make it sound bad.

There's something about this unit that just eminates class.

With the 18V power supply, it has a ton of headroom and no noise (that I can hear).

The tone is really pure. With both boost knobs all the way down, it works mostly as a unity gain buffer. A very good buffer. When I switch the Aguilar in, the pickups sound the same as before, but more clear and hi-fi, thanks to the sudden lack of passive signal loading.

The bass boost adds (you guessed it) bottom. Warm, pillowy, rich bottom. The treble knob adds clean and crisp (but never brittle) highs, perfect for slapping. Many lesser EQ circuits leave this kind of cheesey EQ residue on the signal, but the Aguilar sounds completely natrual. 18 dB of boost is much more than you're likely to need, but it always sounds nice, even at absurd settings. My favorite setting is both boosts up about 15% for a subtle but very tasty "scoop" sound.

The somewhat primitive 2-band boost-only concept may not be for everyone, especially those wanting electronic mid boost. I must not be one for mids, because I don't miss that middle knob, one tiny bit.

Extra bells & whistles my bass lacks, but the tone has spoiled me rotten. I can't stand to work with standard, cheesey onboard EQs, anymore.