Like another reviewer, I installed this on a Loar guitar (a 650) and found that it only just fit - the neck angle on Loar guitars is very shallow, considering they're archtops. Also some problems with the width of the retaining bracket: it's really built for guitars with narrower fretboards, but the Loar has a 46mm nut, so it was a squeeze, but I got it on the guitar eventually. But these are problems with the guitar, not the pickup.
Much, much nicer sound than the stock pickup. I'm playing with D'Addario Half-Round 11s through an AER Compact 60. I tried flatwounds, but the bass was muffled and not well defined. The half-rounds really add some character, and this pickup reproduces it quite sweetly. I would say that, rather than being trebly, it's very very clear, so you get a faithful reproduction of your guitar's actual sound. A bit of care with EQ and you've got a nice, slightly punchy jazz sound. I also tried it through a Roland Cube 80, which is loaded with different options, and got a quite decent rockabilly sound.
Very pleased with this pickup, it's transformed my guitar.