I seem to be the only one singing its praises, but I love the Tate's 'surround' upmix mode. I prefer it to both my SMv1 and QSD-2. It creates a horseshoe-like effect where everything that's hard-panned left or right in stereo is placed discretely in the rear speakers. It really isolates stuff in a way I've never heard any other hardware matrix decoder do. I've had really impressive results with Fleetwood Mac's Tango In The Night, CSNY's Deja Vu, Black Sabbath's debut LP, Dire Straits' self-titled album, and several others.
Regarding SQ decoding, I don't agree that the Involve unit is as good or better than the Tate. I've done a close A/B between the two and I think the Tate gives more separation, particularly in the center front to center back position. Listen to the rear channels only of an Involve SQ decode and you'll almost always hear the vocals leaking into the rears, whereas the Tate wipes them out almost completely.