I remember this feeling I have owned about 12 different mobiles in about 4 years. I got the N810 and that slowed my desire to buy a new mobile phone to 'spec up' because the realization that having a computer in your pocket will always be better than having a 'phone' set in.
With the N900 being a computer and a phone I really have no desire to 'upgrade' to anything else. As long as there are some minor improvements in performance (non overclocked), I think I can stay with it for the next year or so even when the flagship Meego 1 device is announced...well at least I hope so