I bought Z3TA+2 earlier this year and only now got around to delving into it, these are my initial impressions:

Good:

- 2x oversampling and highest precision mode sounds awesome
- performance playing and real time control options are probably the most configurable and advanced I've seen so far in anything
- loads your own wavetables, LFO shapes, arp patterns if you want - yay!
- that arp's really quite nice
- flexible FX order
- useful EQs
- good, voluminous factory content

Bad:

- 2x oversampling and highest precision kills CPUs dead, compromises must be made
- Badly parameterized, inflexible reverb that as a result doesn't work in many situations because it's impossible to dial in the sound you want (for instance, predelay and room size are not configurable other than by choosing one of 5 reverb types, and then they're linked to each other so you cannot have a long reverb tail without a long, mushy predelay)
- the arp screws with playing and testing patches - if host playback is stopped, for example, the arp will not play the sequence but just one note, and unless you know what's happening it feels as if the patch is inexplicably monophonic. this is exacerbated by the overreliance of the factory content on the arpeggiator
- modulation usability kind of breaks down with very small values (like those necessary for subtle vibrato)
- unintuitive modulation lingo has to be learned by heart and is otherwise pretty much unusable without the handbook (you're constantly going like, wait what the heck does BLINEAR- mean again)
- patches and especially modulations can get incredibly intricate (which is great!), but there's no way to comment patches or at least name modulations sensibly, which limits preset usefulness (especially in third party content), re-usability and accessibility.
- distortion effect is weak - this is partially offset though by the waveshaper
- delay time counting seems off by a factor of 4, at least compared to my host and other synths like Massive. Perhaps it's not a bug but unintutive naming, like "1/4" not meaning "1/4 note" but "1/4 of the length of the currently loaded arp pattern" or something
- the GUI has these multiple choice fields everywhere, you're supposed to left click to go to the next value, right click to get to the previous, and that is aggravating. Impossible to know how many choices there are and what exactly you're going to. Some fields, with no discernable pattern, get a nifty and useful dropdown menu in addition, but most don't

I guess that list looks overall more negative than positive, but I wouldn't say the points were all equally weighted, much of the "bad" stuff is workflow related and doesn't impact the sound much. I'm pretty happy I picked it up and it's definitely possible to get kickass sounds out of it. I won't however do what I did with Massive, I think (which is build a 500+ preset sound bank to sell). I saw a post here talking about the standard oscillator octave being lower than on most other synths, and I definitely hear that - I usually design at C3 as a reference point, but with Z3TA+2 C4 is more appropriate. It should be fairly easy to shift all the oscs 1 octave up in the default patch though. Also, to me personally the live performance capabilities, really one of the strongest points of the software, are perhaps less valuable than to others, since I am not a great instrumentalist and prefer sequencing and automating asynchronously to performing and recording live.

Overall (preliminary) verdict: 7 out of 10 cats
 
(if any of my criticisms are rooted in ignorance, as they may well be, please speak up! thanks :))

z3ta+2 is a quite fun synth and i agree with some of your issues, the one thing i'd like to comment on: 
"delay time counting seems off by a factor of 4, at least compared to my host and other synths like Massive. Perhaps it's not a bug but unintutive naming, like "1/4" not meaning "1/4 note" but "1/4 of the length of the currently loaded arp pattern" or something"
anything that has those sync options (and this is specified in rapture as well) is around the definition that the value 1=1 beat.  this is to be flexible with time signatures not based on quarter notes.  so in 4/4 time, 1=1 quarter note, 1/2=an eighth note, 1/4=a sixteenth note, 2=two quarter notes, etc.  
it's a bit confusing at first, yeah, but pretty flexible.

Ah! That clears that up. Thank you!

no prob.  the other thing to realize is that all cakewalk synths operate under the assumption that the low c is c-1.  this can make it a bit difficult to keep in sync with, say, native instruments synths that use c-2 base.  if you have your base octave for pitches set to -2, you need to remember that or set up a track template for cakewalk and sfz synths that have a transpose value set.  this is the easiest way to make everything play nicely together.

I wonder why that is (that, AND the note length/bar fraction thing you explained earlier)... what positive consequences there were that outweighed the negative impact of going against conventions in the minds of the people who made these decisions. Or whether there really are environments in which one could have grown up and that would have made this stuff feel right. ;)

wayfinder
- the arp screws with playing and testing patches - if host playback is stopped, for example, the arp will not play the sequence but just one note, and unless you know what's happening it feels as if the patch is inexplicably monophonic. this is exacerbated by the overreliance of the factory content on the arpeggiator

Which host(s)? I cannot reproduce this issue in SONAR X3e. Whether the transport is running or not, the synth plays the same.

Ableton Live 8

This is the first report I have seen on this issue. It may be peculiar to Live or the installation. I do not have access to Live to test. I suspect others do though. May be useful to indicate which OS is involved. The plug-in should work the same as the standalone.

XP. I'll try on a Win 7 machine later

The Tempo convention seems pretty standard these days and Z3TA from René is as about as old Kontatk.  Sure beats using your ears for sync as in the old analog days, and certainly isn't inventing a square wheel.  There are lots of ways to skin a synth, from sync to knobs or sliders?