I like my Sony PRS-T1 very much. Nothing bad I would make a lot of noise about. Library management on the Reader could be a bit more flexible, and I suppose the OS in general could be a bit more refined.
I am happy I bought it despite my general distaste for e-Ink. I like the Rocket eBook for reading in bed without an external lighting source. I held off for quite a while hoping for a good hybrid screen along the lines of Pixel Qi but there doesn't seem to be much happening there.