At the moment there are only a very small handful of apps I would like to see on the n900 that are currently available on the iPhone

Stealth Tones (I work in schools and the kids can be a nightmare sometimes LOL)
TomTom ( call me old fashioned but I prefer it to sygic)
Nasa App
and then things like tvcatchup, iplayer and the new Formula 1 app (which is pretty cool on the iphone)