Can't explore files on my Sony Xperia U using my Ubuntu 12.10 laptop
I have found the simplest method, with both my Samsung Galaxy Tab2 7.0 tablet and Galaxy S3 Mini smartphone, is to use SSHDroid (on the Android device) to provide SSH server.

Google play > SSHDroid by Berserker

Then I simply connect from Nautilus using SSH, over WiFi. This is plenty fast and I can bookmark the links for re-use (provided the IP address stays static). After first use, I simply set a static IP on my router for those MAC addresses.

I have also used a terminal, for an SSH command line session to the devices. This also just uses the SSHDroid service.