I always liked the sound of EMG's, especially the active ones. I'm happy I put these H4's (yes, two H4's, not an H4A in the neck position - I wanted a consistent sound on both pickups) in my JTV59. Nice, even response across the pickup, nice sustain. One problem... and maybe this is because I installed H4's... the neck pickup is too deep and bumps up against the guitar's cavity. As a result the pickup is not parallel to the strings but higher on the neck side. Minor problem and doesn't affect the sound nor playability. I suppose I could "dig out" the cavity but opted not to.
The install was fairly easy (but I should mention I do all my own guitar work so easy to me might be a challenge for someone else). On a JTV59 one is dealing only with 2 wires to the circuit board for each pickup so it was just a matter of figuring out which 2 pickup wires should be soldered to the board. I tried a couple of different combinations and once I settled on the configuration I liked best (there really wasn't much difference between the only 2 possibilities), I soldered them in. Voila !