Actually I'm the "close application after you're finished" type of guy, even on my desktop. But I find myself using multitasking on the N900 even more than on my desktop PC. One reason is that compared to a full-blown PC with DSL-connection, my N900 on a more or less reliable 3G/2G-connection is relatively slow. So whenever I start doing something that I know will take a few moments, I use the time doing something else... Start writing the next mail when a website refuses to load instantly... Check RSS feeds while application manager is busy... and so on. It's less that I really need to do 2 things at a time - I just use this strategy to avoid having to wait. (And yes, I know that both activities are being performed by the same CPU, making me wait even longer... it's a psychological thing.)

Of course there's other situations when I do "real" multitasking, like when I copy part of a web page, send it by mail, then read on... (did that just a few hours ago)... Or that other occasion when I had a chat going on and looked up the café the other person was at on Ovi Maps (satellite image was useful), then getting the time table and directions from the fahrplan application. That was a nice example, btw, as it really didn't interrupt the chat experience at all and I could just say "Oh, sure, I know where that is. It's right at Augarten park, isn't it? Could be there in 35min or so."