The ear speaker is very clear. I don't use the speakerphone for calls, I use it a lot to listen to tunein radio while I shower and it's ok. My wife has a Motorola Defy and it's much louder than the Galaxy S2.
What can I say, it works but don't expect to much from it.
The included earphone do sound great for multimedia, which you should use in the first place to save some battery juice.
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