First short Soundblaster ZxR impressions:
SBX is NOT a relabel of THX Tru Studio Pro. It is much better, especially in Soundstage (both depth and width) and by the fact that it renders much more accurately while being very truthful to the source compared to other solutions, especially CMSS-3D. You'll appreciate this a lot.
One important thing I found out is that if you use OpenAL in any form, if "naturally" or through Alchemy, SBX is turned off and you don't get 7.1/5.1 downmix but a "standard" 2.0 headphone mix. Maybe it doesn't happen to you but it does in my case. I tested it with Mirror's Edge, Prey, Guild Wars, Bioshock. After getting suspicious during my testing I went ALT+TAB onto the desktop and opening the SBX panel I found out that SBX was turned off. I turned it on again, switched back to the game and voilá, Everything working wonderfully and actually quite good.
I am positively surprised by this new card and while I haven't studied older games enough to make a final overall conclusion (regarding OpenAL) I advise everyone in search for a new gaming card to get a Z-series card before anything else, depending on the amplifier needs.