I will add, in the circumstance that you have a few guitars and a few decent pickups (BK or otherwise), a situation I think most of us are in,
You lucky guys... I started playing guitar in 1979, got my first _real_ guitar in 1989, and only had a second one a few weeks ago. And I had both for dirt cheap (not much more than a BKP set each...).
even if you have a *good* sound out of all of them -
DONT settle for the first acceptable combination. Try different combinations. Move your pickups between your guitars to find what works best in what.
Given that one of my guitars has humbuckers and the other one single coils, I may have a hard time following this advice 
More seriously: it's surely a good advice for those that can afford that much gear - and I would add : then post here and tell us common mortals about your experiences...
I dont mean to be a dick, making fellow members that dont have as much stuff feel bad, but going by discussions here and the various 'what stuff you got?' threads, its true. Most people here do have a range of gear, and I was tailoring my advice to the largest proportion of the audience.
p.s. the means to aquire what you want are rarely achieved by good luck! Such is the nature of good luck - it favours so very few frequently. I have a good job and a make no apologies for it, I've earned it and earn my wage. But if youre insinuating that we're rich and youre not so we've got stuff - there are guys on here that dont earn much but save it all for gear. We're gear whores to the point of religious zealotry :twisted: As an example, theres a chap here, superb guitarist, whos a barman with a vh4, elmwood, 2 blackmachines and a nathan sheperd, that I know of. I dont imagine this is atypical of the board. We're just obsessive :)
But, yeah, more seriously :) I'm reluctant to divulge
too much about my experiences with different guitar/pickup combos because my experience, of some mere dozens (not all mine ;) I do guitar teching as a small sideline) I can only relay the broadest generalities, and I have already done so. I dont want to go into too much detail lest my isolated and limited experience be contsrued as anything resembling a 'rule', because there arent any. There are, as Ive said, guidelines that you can use as starting points or best guesses. I've given advice to people here on what pickup to get and they've returned later saying that its not quite right. (Not all my doing and not singling me out, but my recommendation being one of many and not being right for the persons requirements). I know how poorly transferable one persons knowledge of tone is to another. Its the same with any subjective experience. We do our best, and I think most of the time it turns out well, but I dont really like the basic objective of this thread because if it all went to plan and we had a list of wood/pickup combo dos and donts then it would do as much harm as good. These things are not so ridgid.