I upgraded from the S4 which is a great phone. I read extensively before upgrading and was a little hesitant from all the negative reviews about battery life, no sd card and no changeable battery. I have been pleasantly surprised! The S6 battery is as good or better than the S4, everything is so much faster, display is wonderful and camera excellent. I am very happy with it and really at this time have no complaints. Best phone I've owned!
The new Samsung S6 is lighter and fits the hand like a glove. The response time has greatly increased. The screen is very rich in color. The amount of apps for the phone has greatly increased. I was in the market for a new phone and my choice was a Iphone until I researched the Samsung S6.
I held onto my S3 because it worked perfectly. Finally gave in and 'upgraded'. I haven't run into much to consider an upgrade. There are several things I like less. I've found no way to customize the notifications/vibrations (email vs text vs calendar vs . . . ) as was possible on the S3. I don't like the inability to expand the memory or replace the battery if it goes bad. The camera seems to be a bit of an upgrade. Not really happy about my decision to upgrade now rather than wait for something better. I do like that the speaker is not on the back and that the primary button is down a bit from S3 (the S3 is almost impossible to hold without pushing the button).