Answer: Yes, if you have money to burn, or if you're the type who fall for "no money down" pitches only to find out you can't afford the monthly payments.
Listen--I'm sure the new iPhone 3G, which is now within 24 hours of being in the hands of first adopters, will be a fine phone. The speed and GPS features will be great. But that's about it.
FreeiPodGuy just picked up a shiny new (old) first-generation iPhone. Since I'm a roboshopping craigslist-hacking cheapskate, I was able to nab an 8GB iPhone for just $130. Since I use T-Mobile prepaid, I pay just 10 cents per minute or SMS (and I sometimes can go an entire week without making a call without even trying). So my first two years of ownership, including the cost of the phone itself, will cost me less than $400. iPhone 3G buyers will have to pay about $2,000.
And that's assuming you're in the USA, where AT&T's charges, considered sinfully usurous by locals, are practically a bargain compared to insane rates charged by monopoly holders in Canada, Europe, and elsewhere.
My downside? I have no GPS (which doesn't bother me since Apple has prohibited developers from creating the only GPS app I care about--a turn by turn navigator), and I have to wait until I'm in a Wi-Fi hotspot to use internet (which also means I would get no appreciable speed increase with the 3G, since I will not have had to tolerate Edge speeds anyway).
So what does all this mean?
It means that if you have a lot of money and just have to have the latest thing, trot along to your nearest Apple or AT&T store and bend over. If you want an iPhone that won't cost you an arm and a leg to use, there's always eBay. (There's a reason used 8GB iPhones are still averaging $385 on eBay.)