I have tried Kyma with the Mackie (Onyx) Blackjack and use the two together quite often. I have never had any problems with it either within Kyma or Windows, or Linux for that matter. It's a very stable, albeit simple and basic, interface. It works well. If you're after something basic, the Roland (Edirol) UA-25EX also works with Kyma, though SS are yet to implement MIDI on it. Both of these are relatively cheap and accessible.