It's true that the kernel driver doesn't support full duplex which translates to a lot of trouble with Speak Freely. I've had good luck with the older Alsa 0.5.12A with my SB AWE64. This is basically an SB16 with enhanced MIDI capabilities. I had no end of trouble with the newer releases and the developer who I finally got in touch with claimed that there was a hardware bug in the SB16 cards. If that were the case, no driver would work with them. So, if you are going to use Alsa on an old card, stick with the old version. That's my advice.
