Here are interesting technical articles describing some deficiencies in Nexus One's AMOLED screen. Unfortunately, it seems to apply to other upcoming phones with AMOLED screens, including next generation of iPhone. I wonder if Samsung Spica's "Super AMOLED" screen would suffer from the same issue.
And yes, I also noticed that blurry text on my Nexus One. And it bothers me too. So far I only heard on all the popular podcasts (Engadget, TWIG, etc.) how beautiful is Nexus One's AMOLED screen.
I don't have iPhone, but I compared text on Nexus One with the same text on ADP1 (HTC Dream - smaller resolution) and Zii EGG.