I have a massive Lowepro bag that (just) takes all my gear. It's way too big for many shoots though. I can manage with it when I'm doing sports, though moving from location to location can be a pain (repacking) and it can get bloody heavy by the end of the day.
I now want to shoot weddings however, and the bag will be useless. I simply won't have time to dig around in the bag when changing lenses etc. So I'm looking at systems like the Lowepro S&F Belt & Harness set-up, which seems to allow safe and secure carry of two SLRs (one off each shoulder but retained by lapel straps so they don't bash together), plus customisable belt pouches for everything else.
I'd like to hear from other wedding photogs - what do you use? I want to be able to sling two bodies, one with short zoom and one with 70-200mm, but be able to snatch either up quickly.