I own one for my project studio and I love it!
I can record 16 tracks at once no problem on a mac (older macbook 10.4)
Never had a single driver issue.
If you like the convenience of a firewire interface but you still want to mix a bit outside the box and eventually add outboard this is an awesome piece.
You can even record direct out from DB25s to an analog recording device if you wish. But I prefer doing a mixdown in the analog realm and then bringing it back into the box for the bounce.
It is worth mentioning that the 1640I is not a control surface so it won't control events inside your DAW, but the faders and eq if you desire can effect your channels post recording. So if you assign track outputs in your DAW to input tracks on the Mackies individual channels you can print them effected by the analog channel strip. I'm sure there is a lot better way to put that :/
It can also be a great mixer for monitoring. 6 auxes 2 stereo bus. I personally enjoy the tactile advantages you get with this mixer as opposed to the typical rack interface setup with it's own software mixer. Just so much more simple using your hands vs. mousing through menus. That's just what I'm liking about it though.
I highly recommend it! It's just super versatile, very plug in and play, and it's fun to work on!
Hope you can find some helpful info in this trainwreck of a post