Yep me. But never ran 3 stacked 12-3s. Just two 12's and I tried the 2 12's stacked on top of my 15 for ***** and giggles one night. Yowsers....
I think the stacked 12's couple really well and provides plenty of punch and depth. I find the 15 alone goes a little deeper than a single 12 and is a great stand alone solution. However for me, the 15 was missing just a hair of punch for my taste (ymmv) compared to the two 12's. Putting a BA-12 on top was the ticket but I found it very over powering on stage, even in a loud multiple rock guitar project. This was all outdoor gigs this summer.
The 12 on top of the 15 is definitely a monster!
My sound guy was raving about the tone but had me turning down my stage volume compared to what I like when using the two 12's stacked. The rig really throws out far into the audience.
Hope that helps!