Lax, the issue for me would be focus. The camera has great high ISO performance, but arguably not the AF system to take advantage of it where you need to shoot at wider apertures and focus on specific subjects. That's weddings all over, in my experience, unless you want to use flash a lot. Focusing under such conditions would arguably be easier with a Leica, but there you lack the high ISO performance for the shot! The only cameras that combine both strengths are DSLRs.
Yes, there are some weddings being shot very nicely on non-DSLRs, but IMHO the very best - the ones that make me go 'wow, those are stunning albums' - all seem to be shot on DSLRs and I think there is a reason for that.
I've shot with both and whilst I deteste DSLRs for much of my work, for a wedding I would have the same feeling about my Leicas now that I am familiar with what I can do with my DSLRs. Walk out of the wedding and down a street and the DSLR becomes the awkward beast and all I want is the Leica M (or X100)! But hey, you might find it works perfectly for you!