Cactus Music
The term Zero latency is a term applied to all audio interfaces that allow you to monitor the input directly before it passes through the A/D converters. 
It is misused as people see it and think wow that audio interface must be good because it has zero latency! 
Of course it's zero, it's the same analog output that's been there since they first built an audio mixer. 
 
This is then mixed with the playback from your DAW. This is where a good ASIO driver is needed to adjust the timing offset to match perfectly the latency in the system. System latency or  Round trip latency,  is the figure that varies from interface to interface. 
I didn't purchase the Soundcraft board yet, I just picked it as the best of the lot for my needs to replace my old 01V. 
It's not a high priority as the 01v still works but the day will come I would think, that it will die an ugly digital death. 
 
So even without using it I can safely say you'll have proper monitoring and the drivers are reported to be working with Sonar and many other DAW's without issue. I would guess it will perform at least as good as the 2 interfaces I use right now. If one wants better performance then we are talking much more $$ per channel. 

Yes, it's just a headphones out of the mixer board before it hits the converters, but we call it a "feature" because the driver software has to be able to mute the recording path from playback so you don't hear it delayed...the whole point of monitoring at the interface to begin with.  
 
See, I can't do this today with my Mackie 1620.  It has a headphones out too...but it doesn't playback anything over the Fire Wire connection from the DAW once you hit record.  It records just fine, and it plays back just fine..but you can't record *and* playback.  I have to use a soundcard to listen to playback while recording, which screws up the latency adjustments by the DAW as well.  Quite disappointing. Such a simple and obvious thing.
 
So..as simple as this zero latency monitoring "feature" is, you can see why I feel the need to ask anyway.  It would be a deal breaker if I couldn't mute the recording path out of the DAW so I can just listen at the interface.  I'll dig a little more and make sure.  For some reason I thought you had bought it.  I have established a savings envelope with "Soundcraft" written on it, ha ha.