Really bad timing. The USRP is sitting on my desk for about ten days now, but I still haven't really done anything useful with it. This is because I'm still reading up the theoretical background in digital signal processing.
That DSP book I'm reading is a real revelation, though. At the moment I've finished the discussion of LTI systemes and IIR filters, making my way through the z-Transform. It's really exciting, and I'm sure I need more of that kind of stuff :)