I own a Nexus One and absolutely love it, although I do wish I could claim to have a faster cpu/gpu combo like listed in this article, it is no slouch and has been a great phone since I got it a year ago. Because of that I have found it hard to justify an upgrade, even to some great phones like the G2 or the Nexus S, because they don't feel like real upgrades, just small improvements.
I won't upgrade unless there is a Nexus based Tegra 2 or similar dual core based phone released. The only exceptions would be, if my phone died and I needed to replace it, or a nice Tegra 2/3 phone came out that was similarly hacker friendly like the Nexus.
We live in interesting times, and it seems that things are going to get even faster on our phones/tablets. I can't wait to see 2-5 years out.