That's actually what I did. I don't talk to much but I use browser/twitter/rss reader apps+lots of other stuff on N900. Although I have an external battery charger(x-pal thingy) I still kinda fear to be out of power on N900 in the situation I need to call or recieve one. Moreover, I find myself in the situations when I go somewhere outside for a short time but need a phone to make a call(for e.g. a shop) and carrying N900 isn't very handy(thou I like N900's weight)

That's why I have a dumb phone(tiny one so it doesn't take much space and I can put it everywhere).

For N900 I actually bought unlimited data plan. So N900 is now my 2nd PC.

Speaking to the topic, it's your own decision what phone to buy and use. I can't recall when last time I had to speak about things like "look my phone is better/your phone is worse because of bla-bla-bla"...
So I suggest stop bothering about this. If you are happy with it that's enough.