Reply to myself... another preference for my whammy-equipped Strats is locking staggered tuners. The stagger is the main thing - it lets me dispense with string trees, which I consider to be a potential sticking point, and it allows me to do a few bending tricks behind the nut. The locking thing is nice for quick and secure string changes, but is less a factor for tuning stability, as long as the nut is cut well and lubricated. I swore by Sperzels for years but lately I like Hipshot Grip-Lock Staggered Locking Tuners. Easy to install and lighter than the Sperzels. Technology marches on!For my first several years of Strat use I never used the whammy... because it was a hardtail model. I loved that guitar and wish I had never let it go. I kinda wished I had one at the time but I think I understood that it was almost a separate instrument that would need serious study, plus I was afraid of tuning issues. About 8 years later I finally got a Strat Plus with a 2-point bridge and roller nut. I was pleased that it stayed in tune very well even with vigorous whammy use. I've had several Strats since then and currently have three, and all of them with 2-point floating bridges; roller bridge is helpful but not required. This is my formula for success - tuning is always very stable. I've never owned one with a 6-point vibrato bridge.
I figure half the point of playing a Stratocaster is the whammy. I use it quite a lot for various articulations that I can't get with fingers alone. If I'm in a non-whammy state of mind I'll play something else. That said, I'd like to have another hard-tail Strat, but I consider that to be more of a Telecaster with different ergonomics than a Stratocaster.