I have the old Bel Canto Light Link 24/96.
It is a synchronous USB connection. IMHO these are easily supplanted by a good asynchronous USB connection.
I have had great results with the WaveLink HS but if there is one challenge I find, it is the BNC cable. I have a good coax cable but using adaptors on both ends of the coax causes audio drop outs. So I am forced to use the supplied BNC until I can find a more suitable cable.
I think the Wavelink is one of the best performing USB-SPDIF adaptors out there. It might be outperformed by the OffRamp4 that my friend has but I feel that because it supports INT and Direct Mode in Lion/Mountain Lion and Audirvana Plus, it actually outperforms the OR4 in that configuration.
I haven't heard the new Bel Canto async USB boxes (there are 3) but my friend who has the REFLink can't say enough good things about them. And no, he's not a dealer. I like that it supports INT/Direct modes and also has the choice of interfaces (coax/AES and the ST link). If funds allow, I might try that, and ask them for a VBS version so I can use the third DC output from my VBS :D