My Z4 morning arrived yesterday (thanks Ivojo) and while I haven't been able to set it up properly yet (waiting for the ceiling mount) I did whip an s-video lead out from the player and set it up on a coffe table for a quick look.
Remember I only have my old PTAE100 for comparison and have not seen the other new breeds but all I can say is - WOW!
Huge improvement in picture quality - no visible panel structure and much, much reduced screen door, but then that was to be expected.
Very bright picture, in fact, too bright on the more powerful presets in my darkened room (only 2.8m from screen) but I did try some of these with the lights on and they produce a very watchable picture.
It is very quiet (as good as silent compared to my old 100, especially when it was on high lamp power).
I think straight out the box in a dark room, it is a toss up between Creative Cinema and Pure Cinema modes (Creative gives a slightly punchier image) but I'm looking forward to trying some of ROnes tweaks (at this point my wife rolled her eyes and retired to bed

)
I like the lens shift - didn't have to use keystone at all. And I liked the automatic lens cover - quite cool.
Have to say that I didn't notice the auto iris function operating but then it maybe only works in the brighter modes?
Downsides so far? IT'S FREAKIN' HUGE - maybe not that important but compared to the tinsy winsy AE100 in the middle of my ceiling it may take a bit of getting used to.
Also, maybe a strange gripe but compared to the AE100 there are ZILLIONS of parameters to tweak. I think it might be harder to just set it up and leave it (there wasn't really much choice on the AE100) - I can foresee much remote control twiddling and wife rolling her eyes to come.
But the most important point is I'm glad to have my big screen back - was beginning to miss it. I can start to get through the backlog of DVDs now