Re: Heart rate monitor!
1. Android is open source, though the app store, maps and many APIs (location services, in-app purchasing etc) are Google's own propriety parts (and Google are encouraging more 3rd party app developers to hook into the proprietry APIs). Samsung would rather do without the closed Google bits, and has a Plan B (its own app store and its own equivalents to Google's mail, maps, notes etc apps) up its sleeve, but so far it hasn't taken the plunge as Amazon have done. Samsung also have a Plan C - Tizen - but its Open Source status is a bit fuzzy.
2. Battery life is a function of two things - the capacity of the battery, and the power draw of the rest of the phone. The newer Qualcomm chipsets, built on a smaller process, have been found to be more frugal than previous generations. True, some users would benefit from bigger batteries (some Motorola phones offered model variations with bigger batteries) but that obviously carries a size penalty. Personally, I get on quite well with little Li-ion battery packs.
3. Durability? They've made it waterproof! Other people here can give you an idea of how scratch/chip-proof the screens on previous Galaxy phones are. As for drop-resistance, this varies from user to user. If a phone is designed to be used by people who spend most of their day in carpeted rooms, yet you work on a building site - stick a case on it. It's physics- there is no escaping that protection against drops means adding thickness to the device, so it's better to let users add the level of protection that suits their situation.