Awww...

Listen, I'm too tired to read all the other comments, and I'm probably repeating something that someone else said, but hey, you registered, you came here, you posted, you've gone this far- I say give the n900 a few more weeks.. It sounds to me like you're an "advanced" Iphone user (you know your sh*t, so to speak), but that's only because you have the iphone for much longer than you have the n900.. You think when the iphone first came out people weren't showing off their symbian apps against the iphone's?
Most people here would kill for an n900.. you've gotten this far, why not try using it for a while.. Download the haze and butterfly plug-ins (Are they called plug-ins?) so that the device would be connected to msn and aim (Not sure if you know, but these are not external apps, it's integrated in the device itself, and that's what makes it so cool.. Receiving an IM is the same as receiving an SMS).
Download DOSbox and play a bit of heroes 2 or a bit of quake 3 if you can find it.
Download Firefox and surf the web for a while.
Listen to some music, and while you do so take 30 minutes in the applications forum and games forum, or just go to the downloads section and the extras section and see what's cooking and what's already download-able (I'm sure you know, but I'll say it anyway- downloading alphas and betas may damage your phone so be careful what you download).

I know I sound like a nokia commercial.. But that's what I would have done..
I understand you're very familiar with your iphone, and I've got nothing bad to say about it, but you shouldn't be close minded..

And if you've already done these things, and you still don't like the phone, then, by all means, sell it if you feel it's not right for you.

Happy birthday :P