i am now the proud owner of a mackie onyx 1640 w/ firewire. i needed a new mixer and more channels, so i combined both! i have not yet had the chance to REALLY test it but so far i got this to say:
the preamps are noisier than i expected and i am very confused by the fact that 0dB~-18dBFS. it makes sense with recording (nothing can surprise you), but when you playback a normal music-soundfile the meters are just kinda <on>. weird...
however i also noticed that this is really the way to record. it's all easy and fast. drivers made no trouble, latency is short (at least the displayed latency, still gotta test the actual latency), interface is stable. connect firewire, plugin mic, gain, choose channel, record.
and also: the recorded material sounds good. hard to describe really, but it sounds good. i don't have the feeling that i'm limited by my mixer and a/d anymore. the disadvantage of this is that i definately need new mics now
oh and also: this thing is a MONSTER (dimensionally). although it's only 19 inches wide it's very deep. that doesn't really translate through the pictures...