Hey guys. I'm running the GM installed from Monday with a clean install. I must say that my 4S is running like a dream so far. I'm actually very surprised how well it's doing, quite frankly. The OS is as responsive as it was on launch day three years ago. Apps open pretty fast, apps stay loaded in memory much longer than they did for me on iOS 7, and overall responsiveness from Siri to when a call comes in and I'm watching a video or something to typing with SwiftKey...everything works well. I have Background App Refresh on for just a couple of apps (1Password, Any.DO, Dropbox, messaging apps, Mailbox, Pocket, Spotify, and Tweetbot). Location services only for GPS (Maps/Google Maps/Waze) Instagram, and Foursquare. Activated iCloud Drive (I didn't have any docs in it, so I was ok). All privacy stuff turned off (no Share my location, Diagnostic sending off, Frequent Locations off. I've gotten 7 hours out mixed wifi and 3G use (mostly wifi since I have it at home, school, and TWC wifi-finder app with the installed profile, and I noticed I hook on to wi-fi networks a lot as I move through the city, so this may have something to do with the good battery), and considering this thing is two years old (replacement 4S in 2012), that's pretty nice.
All in all, I'd say that not all experiences of iOS on the 4S is horrible. Mine, in fact, is quite exceptional. So much so that my desire of the iPhone 6 is no longer at a fever pitch - I can wait until I can walk into the Apple Store and pick it up with no (not much) waiting.