I have couple of them, bought, collected, etc. So comfortable to have one of these. I have felt somewhat stressed out when I am using mouse/trackball, whereas with rollermouse it kind of feels relaxed. Construction of the newer ones are somewhat better and has a wider slider window.
Regarding the button press thing, if you buy new/with all accessories, these come with some felt/rubber pads that you can adjust to have the keyboard space bar slightly above the roller, so you dont have accidental clicking. Of course the click buttons are super soft due to the roller weight. May need some muscle memory tuning. See, the main advantage is you can keep your palms at any position and still you can roll/slide the roller.
One caveat may be, the horizontal slide is plenty for a large monitor, but if you are using dual setup/high res monitors, then the horizontal end-to-end travel will be somewhat limited.
You can order the laptop version that is little larger than a TKL board, this would solve the desktop space issue. There is another roll mouse like thingy made by another company, that may be a option. Cant remember what is the brand,, but I saw in EBay, cheaper than rollermouse. Have no more info.
Thats it.
