I also have a Z. The keyboard isn't great, but I got used to it. The only real problem I have with it is the shift key. On the other hand, it got the arrow keys right--they're actually full-sized unlike the mini ones that other manufacturers (Apple included) seem to like. I've spent hours programming on the keyboard and it's been fine.
The fans are loud, but only if you use a significant amount of CPU, which I almost never do. If some errant process cough flash cough is taking up too much, I can hear it and deal with it (this alleviates the annoyance a bit).
The trackpad, on the other hand, is brilliant. Using multiple fingers works every time (on Linux, anyhow) and it's actually pleasant to use. I think that all your issues with it would be resolved with Linux; the bloatware is also gone. I've played around with Mac trackpads, and like this one more.
I'm using Fedora 15 with KDE, which is running wonderfully. I had to upgrade one package to get KDE to play well, but I think that's fixed in Fedora 16 which is current.
I have not had any issues with the space bar--my only problem has been with the left shift key.
I have to add that the only gestures I've actually used are multiple finger scrolling, pressing with multiple fingers and circular scrolling (which is pretty cool). I don't have zooming--it tends to annoy me more often than not, so I don't know if that works well (or at all) on Linux.
The fans are loud, but only if you use a significant amount of CPU, which I almost never do. If some errant process cough flash cough is taking up too much, I can hear it and deal with it (this alleviates the annoyance a bit).
The trackpad, on the other hand, is brilliant. Using multiple fingers works every time (on Linux, anyhow) and it's actually pleasant to use. I think that all your issues with it would be resolved with Linux; the bloatware is also gone. I've played around with Mac trackpads, and like this one more.