Samsung phones ship with ROMs that try to remove as much of the native Android experience as possible, and tend to eat battery life for no good reason. Swapping ROMs to AOSP-like experiences vastly improves battery life and performance on many Samsung phones.
Several Galaxy and Note devices also cannot ROM swap at all due to locked bootloaders, which makes that the most consumer hostile thing of all. I'm not sure which models this effects, but it is enough to put Samsung on my forever shitlist.
