Just got a Nexus 7 and rooted it with CyanogenMod which allows you to hotplug USB devices. Supported are many USB DAC's. My HiFiMeDIY Sabre USB DAC works without an external USB hub.
Sound was a little flat but you can use DSP equalizer to make it sound like you like. I use Squeezeplayer and Logitech Squeezebox, or just stream Pandora or MOG.
I'm still a fan of the Raspberry Pi as a source as it is MUCH cheaper but it is pretty cool to have a hacked tablet to use a USB DAC on.
John
Sound was a little flat but you can use DSP equalizer to make it sound like you like. I use Squeezeplayer and Logitech Squeezebox, or just stream Pandora or MOG.
I'm still a fan of the Raspberry Pi as a source as it is MUCH cheaper but it is pretty cool to have a hacked tablet to use a USB DAC on.
John