does anyone use subwoofers in their setup?

[baconbrain]

You need to apply the delay to the fronts, not the sub (assuming your sub is near to your fronts/mains). It's the sub and any DSP in and/or in front of it that "lags".

A stepless phase control really would be best. During setup in my system I've noticed there's a real small "window" where things are optimal, just the tiniest change of the dial would again result in an out of phase setting again. (it's a bit like tuning to a radio station)

If there's no stepless phase control available I'd rely on the frequency amplitude measurements of a tool like REW (sounddoctor also mentions this). There you would look for the highest amplitude at the crossover frequency with the different subwoofer phase options to determine the phase setting nearest to optimal.

Devialet implementing a real time setting of the delay option so that we can change while listening, or even better doing real time measuring would indeed be very useful.

Ok, so in essence phase is another possibility to adjust timing. What throws me off is that one would think if the delay settings were correct to begin with then you could leave phase at 0?
My subwoofer is closer to my listening position than the mains and for that reason I am applying the delay to the preout for the sw.