Can you afford the money to spent on it? Do you have spare time to spent on it? Do you have a phone near by in case you get pissed off by the phone capabilities of N900? Are you curious enough about where the technology is heading to? Do you like to read, test softwares and listen music before you go to sleep. Do you want to bring small support to the freedom of communication in this world.
If you answered yes for all, than do not wait. Conditions may change tomorrow but so one day of your life.
No other 500 EUR device kept me so busy, made me so nervous or happy, etc. like N900, until now. And still has potential as I can see.
I am not paid by Nokia although I own several models and dissapointments, I own and use regularly Apple Ipod/Iphone3G although they are not perfect and cheap, I am not a software developper, etc. I assume to be honest enough but may be a bit too old to be trustful.