mee too! Works pretty good.
Tip 1: wait a minute or so after your computer boots up and you login, before opening sonar. I have noticed if I login and immediatley open sonar, it doesn't recognize the 1884, even though the firewire indicator is lit on the 1884. when this happens I have to reboot.
Tip 2: not sure if this i am the only on with this issue or not, but if I turn off the power to the fw1884, while the computer is on, windows 7 locks and throws some errors at me. this will also cause me to reboot. If sonar was open when I shut down power to the 1884, a reboot is needed for windows to recover the previous session and then another reboot, because it doesn't see the 1884. So I always shut down the 1884 after the computer has shut down.
drivers etc:
http://tascam.com/product/fw-1884/downloads/