Two iPhone 4's and two iPad 1's in the house. Both my phone and iPad are JB'd, both of my husband's are stock.
Security is only an issue for those stupid enough not to read and follow directions to protect themselves, or who download pirated apps. Both categories pretty much deserve what they get, in my opinion. The rest of us seem to manage not to get in trouble with our devices JB'd for years on end.
If I had to go stock, I'd buy an Android instead. There are WAY too many things Apple apparently can't be bothered to implement, and too many arbitrary limitations they impose on my ability to use my phone--like their ridiculous "12 items per folder" limit. iOS 5 adds absolutely nothing useful to me, so I won't be upgrading until an untethered JB is available.
Beta software, on the other hand--no thanks. Been there, done that. I was in the industry for 20 years, and had to beta everything under the sun. My JB'd phone is stable, I'm not voluntarily adding buggy software to it!
My husband, on the other hand, is mostly happy with his fully stock devices and up to date firmware...until he sees some cool feature on mine. He's sure to add iOS 5 the day it comes out officially. He likes his stock phone, and that's totally fine by me.