Activating plugins in multisite

I noticed that Andrea said in one post that it is best to avoid network activation of plugins unless really necessary.

Now I’d like to try out some plugins on the main site — or even on a test sub-site — but that seems impossible. When I go to the plugin interface on the main site, there’s no option to add a new plugin, unless I go into Network Admin mode. And in Network Admin mode, I can only network enable, not enable for main site only.

Sub-sites also have no option of adding new plugins — only the option of activating or deactivating plugins. Thus I can’t test them out there. Of course, I suppose I can test them on another domain that doesn’t have multiple blogs, but is that the only way?

Is that the way it’s supposed to be, or is there something in my setup that’s quirky?