I did a recent adventure race (short one, 3.5 hrs) with a camelbak, and a gel (and a bottle on the bike) and drank it all. I have also used these things on training runs just to get used to them. I have worn the camelbak on 30min runs, which looks silly, and people shake their heads as though I am a lunatic, but is is all part and parcel of training. You wouldn't set off on a race in brand new shoes, or in different shorts - who knows what will happen. I also tested a gel on a 45 min run, for taste and to see if my stomach liked it. Unfortunately it killed my apetite and ruined dinner...