I had my Canon 40D with 17-85 IS
50 f/1.4
and now...thanks to your advice, I am a proud, and a little giddy owner of brand new 70-200 f/4 IS.
I just snapped a few pictures outside and I am thrilled, just what I needed. Even this lens is heavy for me, so no way I could handle anything heavier for random walks, I would get carpal tunnel syndrome in no time. I am not saying it's a girly lens, but it fits me just fine, and I love it after just having it for half and hour. I am going out later on to take some picture to get acquainted with my new lens.
Thanks again to all of you for great advice []