I built a guitar with this pickup configuration. I used a Jackson J-95 (disppointing overall) in the bridge position and a Duncan JB in the middle position.
The JB sounded absolutely spectacular in this position. My theory is that by taking a pickup tailored for the bridge position and moving it to the middle where there's more string excursion, you amplify the amount of signal going into the pickup, without introducing too much muddiness. I found the sound to be very clear and open, with lots of punch and harmonic richness.
Jerry Garcia also had the same H-H-S pickup layout on his "tiger" guitar as Stephen Carpenter has on his signature ESPs.