I know that previously (maybe still current) many Waves plug-ins don't support side-chaining as I'd expect in Sonar. Has anyone been able to use Waves InPhase to line up two snare tracks, or overheads, etc. in a mix? If so, how did you do it? Was it easier to use the plug-in, or to use simple slipping of the track phase?

Admittedly I haven't gone side chain crazy but every Waves plugin that supports it at all has worked fine for me. Mainly compressors and both Riders. I know that doesn't help your question about this specific plug, I was just wondering which ones are failing for you.

Waves Inphase is one of the most useful tools On the planet.  I not only use it to check phase on tracks but ....Lets just say you just overdubbed a guitar track and you got a couple of milliseconds of latency . Sure its souds OK but not as tight as you heard it when recording , Instead of zooming in and dragging the track around .... Just put this plugin on your track and type in -2.00 ms in both settings boxes and presto non destructive track shifting , Tweak until its sounds as tight as it can get .