I've had an Uberkab, but it wasn't loaded with the combo (bought it empty and loaded my silver label G12-30s in there). It was however the biggest sounding cab I've ever owned.... even with those mild 30 watters in there.
Right now I've got a Marshall 1960B and Line6 (V30 version) that I've loaded both in the X-pattern with V30s/T75s. I've been rocking them this way for about a month or so. Jury's still out on the combo for me though. I kind of dug the straight 4 X T75 load as it was. Pleasant, flat or slightly scooped tone that worked well for modern rock/metal to my ears without being harsh. The X-pattern combo isn't obnoxious. I'm just not sure yet whether it's a marked improvement over straight T75s for my purposes.