I got my account activated and have had my first look at G+. I have never used Facebook so everything is new to me. In the beginning the layout was little confusing but is quite easy. Let's see if I'll be using it. I mostly signed up to get in contact with people I don't meet so often. Facebook would be currently much better for that but I don't like their attitude on privacy at all. Hopefully G+ will catch on.
G+ doesn't seem to work well with Nokia N900 default browser. I can see posts, but posting them doesn't seem to work. Neither does drag&drop on touch screen and adding people to circles is hard otherwise. Pop-ups open but are shown blank.
Unfortunately Opera mobile is not supported. I have to check if some other browser solution works better (Iceweasel using EasyDebian?) or if browser identifier of Opera mobile can be changed to cheat G+.
Update: It seems that Macuco browser works somewhat better. It's not perfect but writing and drag&drop are possible and it is available easily from Maemo extras repository.