That's a tough question, spork. Like several others here, I'm on Sprint, and I like it for many of the same reasons. I was a Verizon customer (my wife still is, actually) dating back to the Bell Atlantic Mobile days, but converted to Sprint when I realized that in the New England area they covered nearly all of what Verizon covered, cost significantly less, and appeared to be proactive about offering new smartphone models... this being in the days of the Treo 600/650.
Verizon does rub me the wrong way in so many ways... not the least of which is the smugness they appear to portray in their advertising... they've crossed the line from boastful to smug, and for me that's not a good idea. I did have some customer service issues that weren't handled well, and they cost more... so what did I have to lose trying Sprint?
So yes, I'm with Sprint, and am quite dedicated to them. Should be a no-brainer, right?
Well... I love WebOS. It is a properly intuitive and responsive user interface, and Synergy is a miracle for my calendar. My mobile OS experience includes palmOS, Windows Mobile, and webOS. I have handled Apple's IOS, but it didn't feel right to me, nor did I like the lack of a hardware keyboard (something I learned when the h/w keyboard on my Touch Pro failed). I haven't handled Android, but the impression I get about Android is that it's an OS that you can mold to how you'd like it to work... and quite frankly, you'll need to do that. Sorry, but to me that's just like Windows Mobile, and I couldn't stand how much effort I had to put into making that phone work better. WebOS has the advantage of working well right out of the box, much like Apple's IOS does. Even Windows Phone 7 might also have this advantage. But webOS is definitely my favorite to interact with, and giving that up would be tragic.
So, if my phone were to die today and there were no webOS replacements available (Pre or Pixi, though I'd hate to downgrade to a Pixi on Sprint), I suppose I'd seriously consider the HTC Arrive on Windows Phone 7 on Sprint... but I'd really hate to do so. If that didn't work out, I'd see if I could swing going without a contract on Verizon... though I'd be subject to an ETF on top of it all, so that probably wouldn't be viable.
Tomorrow's another day... we'll see what that brings. I'm also still interested to see what HP is planning to "make it right"... as while my Pre is from one of the final days of sale, I had been waiting for the Pre to reach its next generation on Sprint ever since the first day it went on sale, so I've been feeling the wait for that long. Such is device lust, I guess.
EDIT: Great thread, by the way. I never thought I'd see a useful conversation about Sprint vs. Verizon and webOS vs. Android (or whatever OS), but I'm happily proved wrong.