I usually multitask more* when I'm using the application manager. I just fire up the browser to read something while waiting for applications to download or update.

The kinds of applications i use at the same time: email, web, conboy, media player, VoIP, all IM accounts (MSN, jabber) and a twitter client.

Please, a huge amount of RAM would definitely make things better!

[*] I would very much like to multitask while the application manager is running. However, the N900 seems to freeze while application manger is installing applications.