I've recently gone back to using one of these. It is so simple and the battery lasts for a week. I previously had a low end Sony Ericsson and the current entry level Nokia. I use an ipod touch with a 3g wifi modem for mobile internet. i have a 160GB Classic and a 16GB nano for listening to music.
I'd like an iphone, but I think they are still far too expensive.
It's amazing how durable those old Nokia phones are, you can drop them a thousand times and they'll still work!