Hi, I haven't done OSM for years so the desktop units may have improved a lot in that time. However, I did have one a long time ago, and eventually got rid of it barely used. I didn't find it that stable - with a bit of pressure, it could slide on the desk. Also (I'm 5 foot 7), I just couldn't get myself comfortable - the back of the desk chair was constantly in the way, and/or I couldn't get near enough to get the pressure right. And that's without even thinking about the fact that most office chairs are on casters. Quite frankly, I found it a waste of money, and I ended up having to bring a stool as well for people to sit on, so it didn't even reduce what I had to carry, which was the whole point! If you can afford it at all, I would go for a folding chair and a carry bag. I wouldn't worry about doing it in a separate room - think how successful the OSM people are in Waterstones' and Border's at the weekend!