We don't tout it as much as we probably should, but the Summit Digital Mixer actually has an adjustable delay on every single input and output channel.  That includes all 16 input channels, as well as the 8 multi outputs, the main outputs, and the control room outputs.

To the left you can find an image of the delay function for a single input channel (four channels will be shown on screen at any one time).  As you can see, there's an on button, as well as 3 controls for adjusting parameters. 

The "Time", of course, adjusts the delay time (up to 2 seconds), whereas the "Mix" determines the amount of your mix will be delayed.  Finally, the "Feedback" determines how much of the signal will be fed back through to the channel (particularly useful for electric guitars!). This is the case for input channels. 

Output channels, on the other hand, just let you adjust the delay time alone.  This is all you need, however, as it allows users to compensate for the distance between speakers in larger setups.

Plus, the latest firmware has a new function that lets users switch the adjustable parameter of the delay function between milliseconds, meters or feet.  That takes a lot of the headache out of live setups!