Harry Potter fans...?

From by research, I have noticed that some Harry Potter fans favor the 1st three HP books wheras others like the last four the most. Seveal people have stated that J.K.'s writing went downhill after POA. I, however, disagree. I favor the writing of the last four the most, particulary HBP and OOTP. What are your views/opinions on this, and which books (1-3 or 4-7) do you feel were better written?