EMG has become a large part of a lot of metal musicians sound for many years.
I've tried lots of pickups and making the swap to active pickups was a great decision.
The EMG 81 is a great pickup, tight powerful sound. good response with a clean signal and tight punchy direct sound when exposed to a high gain signal.
The EMG 81TW version of the 81 has a pot that when pulled out splits the pickup so it acts like a single coil pickup. i used this in single coil mode when playing bright clean strumming and acoustic sounds. as with single coil pickups against humbuckers, the single coil mode is quieter than its humbucker mode so it responds just how you would expect it. think of it as an EMG 81 and an EMG SA in one slot
As for installation it was a five minuet job due to the simple non-solder set up. it turned my guitar into a monster that i gigged with for ages, and when i accidentally broke that guitar, the pickup came right out of it and into another guitar.
The 81tw is great if you like the tone of the 81 but want a little bit more flexibility.