I know P90s aren't the first pickups you'd think of when asked about single coils, but I own a pair of Mississippi Queens in a home-made alder/maple guitar.
I suppose their reputation precedes them, and I initially picked them as a big Muse fan when I started building the guitar as a teen.
Though I've moved on to other kinds of music, i must say I'd rather build a whole other guitar to try some other pickups rather than replace them!
To make it brief(ish), they are just full of character. I'm gonna cite a lot of pieces here, but I think it's a good way to get an idea.
Neck pickup sounds like the most deliciously overwound strat (clean at 3:15 in Muse's Darkshines), really woody and sweet.
Bridge is snarly as heck, in such a good way, you can get almost any heavy tone from crunchy (beginning guitar, Queens of the Stone Age live Belfort 2005) to thrashy (Thee Oh Sees - Web).
And middle position gets just the same tone as 3:05 in Muse's Micro Cuts.
If there's one thing I'd still like a bit of, it's the heaviness and thickness that a humbucker can offer. This is probably because I play a lot of Queens of the Stone Age, Led Zeppelin and stuff like that at the moment.
But apart from that, I still love the versatility with the MQs. You can imitate just anything that you listen to with a certain degree of precision.
Good luck with your quest!