Reception with difficult lighting

I recently shot for fun at my friends' wedding reception. The paid photographer was finished for the night so they asked me to bring my camera to the reception. The lighting was very difficult. Basically a night-club situation - super dim with directional beams of bright light. I used my Sigmalux the entire night with my 5D at 1600 ISO. I shot about 100 frames. Many were decent and meaningful to the people involved but not very interesting. These two are my favorites from an artistic standpoint:

Friend of the bride -

f1.4 1/80 ISO 1600 doesn't sound too horrendous.

That said, the first photo really doesn't do anything for me. I assume a bridesmaid...holding a few drinks not looking too happy. Looks underexposed as well.

The second image is a nice moment captured but it looks soft, and processing is funky, and also looks to be underexposed.

sounds like every wedding i shoot
this is where flash knowledge comes into play.
to make sure i get the shot i usually shoot 500iso 60th at4.5 with flash usually bounced off the ceiling
with such a low ceiling it would work well i bet

I tried some flash, it didn't turn out well. Or at least it didn't turn out in a way I like. The ceiling was very low and the room was just ugly in general. It was converted to a wedding factory from a roller rink in the mid 90's. Super gross.

nicksan is right, they're not great photos. They just happen to be my favorite two out of a night where I shot a bunch. I can do better, this was just practice. Too bad my friends don't get married in nicer looking, better-lit places!

I prefer the one with my friend and his mother in B&W. Some friends of the bride talked me into the semi-desaturated color.

that venue doesnt look difficult at all.. you just need a flash.

Like the B&w version much more than the one in your initial post