I've had trouble with my 6 Plus too. Can't wait for the 6S to come out. Going down in size and hopefully it won't be as buggy. I've also lost some trust in Apple's hardware with this device. Luckily my iPad Air 2 is phenomenal, despite not working properly with BT drawing pens.
Is the S model always that much better? The 3GS was a big jump, but they kept the same speed for two generations. The 4S was okthe main improvement was the camera. I've owned every model except the 5S, but I've used the 5S plenty of times and it didn't seem all that better than my iPhone 5. I still think of the iPhone 5 as being my favorite iPhone of all time. I'm sad that I sold it. The 5 was really stable and still fairly fast when I sold it right before the iPhone 6 came out. Touch ID is nice, and the new cameras are nice, but the iPhone 5 was pretty awesome. Maybe I should have just purchased a 5S instead, lol. But I did want a bigger screen. I just got one that was too big. I think 4.7" will be a good middle ground when I get the 6S. After the buginess with my 6 Plus, the 6S can't come soon enough!!