A lot of people have commented on the decision to go for a sealed-in battery. However, this is common to a lot of manufacturers (and it doesn't appear to have hurt sales of the iPhone!)
A replaceable battery has two advantages:
1. You can carry a spare and prolong use.
2. You can put another one in when it wears out and keep your phone for longer.
But, here's the thing, how many people actually do that? Long ago, I used to carry a spare battery because I could get through two in a day - and they were ni-cads, so needed to be run down each time. Then I got a Nokia 6110 (yes, it's that long ago) and found I didn't need one. Even with intense use, most smartphone batteries will go a full day unless you're in an area of very poor signal, which is the main depleter.
The lack of an sd card slot would be an issue for me because I find it a convenient way to transfer content from one phone to another. There are other ways, though, and hooking up to a pc once every couple of years isn't a major issue. As I understand it, the S6 is going to have a 32gb in its lowest configuration, so the issue is, in part at least, addressed.
The big one for me is the lack of wateroroofing, just when everyone else has latched on to it. If you're producing a phone with a fixed back and no sd card slot, how hard is it to waterproof it?? Especially when you could do it with those options in place.
