glad i saw this thread, as i'm doing a marathon in 2 weeks and they only supply water, so i was going to take my (small!) hydration backpack...i've got used to it and now don't notice it....my dad is convinced that i'm not allowed to do this, his reasoning being that he did 2.30 in the 1980 london marathon without drinking during the race apart from a sip of something someone handed him that he threw away as it was salty....not quite sure i get this....but hey, each to his own!
i noticed someone was taking the p*** out of backpacks, but i kind of like mine....got used to it from having to run into work and carry clothes and shoes (and i've been known to do this for a 20 miile run ;) and actually my bigger one (about 25 litres) is far more comfy full of a day's clobber than my tiny one (3litres) is with just some squash and chocolate in.....now got a not quite so tiny which is perfect....bit like getting the right shoes...trial and error! ok, i'm being boring.....started off talking racing, then ended up defending my macpac....
oh well....