The Audiophile USB I use goes up to 24/96. I've done a lot of A/Bing between 44.1, 88/2, and 96 and I still can't make up my mind if there is any real difference between them with the Benchmark DAC1.
USB potentially has a huge advantage over toslink, s/pdif, and AES/EBU because the data can be transmitted to the DAC asynchronously (i.e. without any timing information...it is sent to the device as needed, presumably when its music data buffer is running low). This is the future, and you can make a very strong argument that, once we have high-end DACs that accept an asynchronous input, computers (or music servers or any other device that can asynchronously transmit lossless music data) will be inarguably the best transport.
One could already make the argument that computers are the best transport based on the fact that 1) a computer with 1000 CDs stored on a hard drive is incredibly powerful and convenient for music lovers with large music collections, 2) reading music data off a hard drive is much, much more reliable than a transport trying to read it in real-time off a CD (once you try to losslessly rip CDs you'll quickly learn just how flaky and unreliable CDs are if you want bit-perfect data), 3) with a "jitter-immune" device like the Benchmark DAC1 the supposedly jitter-prone transfer of data from the computer to the DAC is not a problem (there are ways to overcome this already, like the externally-powered USB and Firewire "sound cards" that many computer users are currently using), and 4) the wide-array of digital equalization and DSP options (which are surprisingly powerful, effective, and fun to play with) available to computer users makes their downstream high-fi equipment sound even better.