I posted about the G83-8308 keyboard before: Cherry G81-8308 Keyboard.
I did not look at the thread before posting this one, but after looking for it now I see that I already posted the pictures of the two keyboards above in there.
That should take care of the review of the old G32-8308 as such. I do not have one of the G86s yet.

To your specific questions:
>> How's the software? Easy to use? Enough features? What features?
The software is basic, without any eye-candy. It does the job though. Keyboard layouts can be saved and loaded. That includes programming that has been created on the fly.
Keep in mind that this stuff is targeted at professionals who set this up for the commercial end users. The software is functional and has it's windows help files, but it is not overly ergonomic.
The above is regarding a software package from back in 2002 for the PS/2 8308 though. I am sure that by today there is a new and improved version.
At http://www.cherry.de/english/service/download.php you can download the software package and manuals if you want to give it a look.

>> And how's the hardware? What kind of buttons (tall or low laptop-like)? Ergonomy? Etc. Ohh, and can you reprogram all the "normal" keys on the SPOS G86-61400, so ie. the Windows and Caps Lock keys could be used for spells rather than.. well, being in the way?
These things are build to last. Full size keys with full depth keystroke. The reason I would want to go for a newer G86 is that the programming via USB is faster (PS/2 takes 2 minutes or so due to the low bandwidth) and that there are no gaps between the number row, the function key row and the additional keys. On the G83, the only keys that can be programmed are the two additional rows on the top. All other keys have normal default function. For the G86, I expect the one with legend able keys all over the place to be fully programmable, while the one with printed keys will have only the keys on the top programmable.