I don't have a problem with my D90's noise at ISO3200 either. In fact, I continue to be blown away at how good those high-iso shots usually look. Sure, ISO3200 shots are noisier than ISO200 if you pixel-peep, but never to the level that I think, "drat, shoulda had a D700".
The point you raise is true of any product. Be it cameras, cars, houses, espresso machines, shoes, pens, or stereos. Is it worth it to you to spend the extra $X to get what you think you need? Some people are happy in Honda Civics. Others require a 7-Series BMW or an S-Class Merc. Those demanding a 7-series might look at a Civic with disdain - "how can you possibly enjoy driving that?". Where the Civic owner might reply, "it gets me to the same places your 7-series does". Some people are happy with the included headphones that came with their iPod, while others demand $1,000+ ones with dedicated amps. It's all a question of value and what matters to you. There are no right or wrong answers.
It's the same with cameras. You can spend $1,000 on a mid-range DSLR like a D90, and you're getting a very good camera. Much better than what most people use to snap their photos (who are using camera phones or $150 P&S's). And it's easy to forget that when you're pining over the latest Dxo measurements of that new lens you want. But like most things, a $1,000 camera isn't going to perform quite on the level as a $3,000 one, and likewise compared to an $8,000 one.
So if you can afford it, and you find your techno-lust inflamed by it, you might as well pony up and spend the money. The soon-to-be-released D700 replacement will likely cost around $3,000 and will almost certainly be an amazing camera. If you've got the cash, go for it. Going back to the cars analogy, it's like deciding that spending $x for the leather interior or the bigger engine is worth it. If it is to you, nothing else will make you quite as content. In a year or two or three, you probably won't miss the few thousand bucks that it cost you, but you have the happy life-experiences gained from those extra "doodads" that you paid for.
I too, look back on some of my earlier digital photos and sometimes think, "man, if I'd had a DSLR (or that lens, etc), I could have better-nailed that shot." But you know what? I also think some of those old P&S snapshots have charm to them. Just the other day I was perusing a couple of albums I took with my old Coolpix 995, many years ago. Kind of amazed at how great a lot of those photos are. While certainly nowhere near the IQ level of the D90, they have their own unique "digital patina" about them that made me remember the joy of buying & using that camera. Sure, the blues are noisy and the AF sometimes missed, but it captured a lot of great memories. And I think, in the end, that's all that really matters.
Good luck!
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D9O, P6K
