Well remembered Karen.
I did UY alongside the Xtrain 90 day rotation - but started UY after the first month. I then moved on to STS and finished up UY whist doing meso#1. It worked very well. I did Xtrain or STS in the morning and UY in the evening. It was a big time commitment, but I ended up about as shredded as it's possible for me to be! The only thing to watch out for is all the vinyasas when your shoulders have already been worked. 5 chatarunga push-ups seem like an eternity when Cathe has had you doing front raises earlier in the day! On my non-Cathe days, I did the Yin dvd, so that I had a real rest day.
At the moment I'm strength training (much lower reps than Xtrain or STS) and doing yoga every evening (almost) - but only 30-40 mins of yoga. It's feeling like a pretty good balance. The yoga I'm doing isn't all as intense as UY, although I try to mix in different 'styles' of yoga.