new mbed was on its way. It's still in beta, but I was lucky enough to be selected for the beta program and I am starting work on my project.
First impressions are very positive: the instructions on the mbed site are very clear. It took about two minutes to use the cloud-based compiler to create the obligatory led blinking program and then drag the binary file over to the mbed.
Now to work through the examples and test it out as a USB device.