Re: Is a strat bridge pick up actually usable?
It's extremely usable – just not for what you want to play, I guess. I think they are awesome, brutal, screaming, crunchy, crashing rhythm pickups...and great for stinging leads too. They're like heaven pushing a low-to-mid wattage amp into natural overdrive, and due to their inherent clarity, they're also a great base on which to build a highly "effected" tone without getting mushy. They aren't too much unlike a Tele bridge pickup IMO – different, yes, but close enough that I like using them for the same basic things. It's a bit rough through a clean amp and/or without some richness added via tone knobs or whatever other kind of e.q. you've got. Here's a hint: try it through an amp without much headroom, like a Princeton or Ampeg Jet II...and play with a heavy right hand. Think Pete Townshend, Malcolm Young, etc. right hand.
To me, the least "usable" Strat tones for what I play are the notch positions (N+M in parallel and M+B in parallel). I prefer a simple 3-way switch on my Strats (N, M, B), or else some kind of alternative 5-way switching scheme that replaces the standard notch positions with something else. My favorite alternate is for position 4 to be B+N, and position 2 to be the bridge pickup through an Eldred-type Esquire tone circuit.
