paper reviewing

I always wonder: how long does it take for the average university scientist to review an average paper. Not a paper that can be published without comments, but a paper somewhere between minor and mayor revisions. A paper where one has to check a few of the citations, because they seem to be out of place or you are not sure what exactly their statement is. A paper that is not so well and fluently written, so that one sometimes stumbles over a sentence and has to re-read a paragraph to grasp the meaning. How long does that take?

I talked to a colleague about it and he at first said: one hour! Then he corrected himself and mentioned that it might take a bit longer than that.

For me it takes about 5-6 hours stretched over several days. From reading the manuscript for the first time to get a general impression, then re-reading it to make comments, mark paragraphs and download citations I'd like to check, to finally writing the review. Some journals allow you to see the comments of the other reviewers (which I think is very useful and I learn a lot from that) and usually my comment list is 2-3 times as long as theirs. Does that mean that I am too picky? Or still too enthusiastic about the peer-review system? Do I invest too much time in the paper review?

I'd love to know how long people in the blogosphere take to review an average paper, which is somewhere between minor and major revisions. How long do you need for that?