Well, I don't think a 1g iPhone will be future-proof. It may not be obsoleted as frequently as the various iPods have been, but it will be soon enough. The N8x0 is sufficiently open (and Nokia plays a sufficiently low part in development) that loss of Nokia support for the N800 will not leave you with anywhere near the drop in utility.

Like you said, the answers here and on the iPhone forum will both be pretty seriously biased. But I think the iPhone is a good choice only if you want something fun to use that does basic phone, internet, and media playback. If you want anything more I'd go for the N800/phone combo. Understand that it is not polished; everything is a little rough around the edges. But it can do much more than even a jailbroken iPhone, and you don't have the hassle of trying to stay one step ahead of Apple when jailbreaking it, etc.