I just switched from the Note 3 to the Galaxy S6. So far, I'm overwhelmingly disappointed with this phone.
Maybe my expectations were way too high. I expected the S6 to be a super-improved, smaller Note 3. What I got was a hybrid Android/iPhone-wannabe with a terrible battery life.
Seriously, my battery must be defective. I can't get more than 7.5 hours out of a single charge! I've had that Samsung Push Services update installed since yesterday; it doesn't help at all. Granted, the first day I was using it heavily as I wanted to explore the phone and tweak the settings (which are severely dumbed down, by the way). However, this morning I turned my phone on at 6:30 AM with 57% battery (I turned it off last night before going to bed). After searching for an app on the Play store and sending 3 text messages, it had gone down to 54%. From 6:30 AM to 6:34 AM, my battery went down 3%. How is this acceptable?! It's now 8:11 AM and I'm down to 42%. The screen has been off for the majority of this time and I've sent maybe 10-15 text messages max. My girlfriend's iPhone was off the charger at 7:10 AM and at 7:45 AM she was still at 100% battery.
Personally, I will be returning this phone and looking for a better one this weekend. I got the S6 because I was so satisfied with my Note 3, but this time I wanted a smaller phone. Now I'm going to have to look at some Droid or Windows phones, because I refuse to go back to the iPhone. I guess now I can (unfortunately) add the Galaxy S phones to my blacklist, too. :'(