For a fair cost comparison:
32GB iPhone 3G from Apple in Oz costs A$1040, which is about US$775 +tax.
That's about 10% more that the street retail price of the N97, so I expect the N900 to be similarly priced, if it sells here, and cheaper online.
The 32GB iPhone is "free" on a 24month plan with $2736 min. spend. So that's a huge subsidy, but if you got an N900 and used VoIP, you'd only need a $15/month 1GB data plan. Not much room for a subsidy in that :-)

I see the N900 does 850MHz EDGE. How acceptable would that be in North America as an alternative to 3G?