Comment 136 for bug 903422

Dirk, As discussed above, mtpfs will never work with an Android 4.x device due to how it uses libmtp. No updates to libmtp will ever change that.

As for your mtp-detect error, that's likely due to another application already talking MTP to the device (eg: if you'd attempted to mount with mtpfs, or if gvfs ptp was trying to communicate with it - which will happen automatically if you have a default Unity desktop, or if gvfs mtp is communicating with it, if you're using my version of gvfs). The MTP protocol only supports one application communicating with the device at a time, so if another one tries to do connection initialization, the device gets confused and can respond in fairly unpredictable ways.