Well after some wiring hassles, I finally got the Mule installed and running in my one pickup Gordon Smith. I got the coil split version, and here's the review.
Pickup height is very important as I tried for a while to get the sweet spot. Too close, and the tone gets too fuzzy - too far away and the output drops a bit too much for my liking. I settled on 2mm from the strings on both the bass and treble side. The result? A classic rock tone through my GH50L :D
The Mule has the trademark BKP clarity as I've heard on my Riff Raffs, and a nice treble cut without being too much. With the wiring on the GS bypassing the tone control when it's on 10, the tone is about as cutting as I'd want. Rolling back the tone to 8 or 9 gives a more Gibson-like tone with a few of the highs rolled off. This lets the midrange show through a touch more and works really well for chunky chords or full leads. Rolling back the tone even more gives a non-muddy full sound - kind of hard to describe but similar to a neck pickup tone.
With the coil split on, the same basic tone is still there but obviously thinner. Roll back the tone and volume pots a touch and you can get a nice Gilmour-esque vibe going on. Very useable for cleaner rhythm lines. It's perfect for "Dancing in the Moonlight" by Thin Lizzy - coil tap for the verse/chorus and humbucker for the solo. Lovely!
Compared to the Riff Raffs, the Mule is exactly what I hoped it would be - not as aggressive and with a more noticeable midrange hump. In a Les Paul I think the maple top would work against this giving a more even tone if that's your bag. I prefer the midrange coming through more, so it suits me just fine!
Compared to the standard Gordon Smith pickup, the Mule is WAY ahead in terms of build quality. Everything is immaculate and perfectly lined up, the BKP logo is engraved on the bottom and the Mule just reeks of quality. By comparison, the GS pickup looks thrown together while suffering from a hangover! In terms of tone, the GS pickup is more similar to a Riff Raff I guess with a more biting treble. It also doesn't have the clarity of the BKPs as you would expect. They're not bad though, but a BKP is a definite upgrade and finished the guitar off nicely.
Unfortunately, I've been sent a Mississippi Queen without four conductor wiring so I'll have to send it back and swap it. Some error somewhere between Chris at Guitarzone and Tim, so you'll have to wait for my review on that I'm afraid! Gives me more chance to enjoy the Mule I guess!