I've used foobar2k on Windows for years because it's the simplest, fastest and least cluttered audio player I know of.

Please stick with these principles for the mobile version, and do not force social or cloud integration upon the user. I would like to be able to disable them entirely, and use foobar2k for what it was meant for - playing music - without any nag messages telling me it'll "improve my experience" to sign up for this or that, like most apps do these days...