My generally feeling on the N900: awesome hardware, awesome OS, but some apps are missing (e.g. a good countdown timer), some apps are pretty rough (e.g. the Ovi Maps app is not Nokia's latest best version for whatever reason) and some apps are still buggy.
Of course, apps will be written, polished up and fixed over time.
I would say the N900 is still in the "early adopter/geek" stage and the really average consumer might be advised to hold off for 6 months.