I have the Sigma 30mm F1.4 which I use for exactly this purpose (though I call mine a "pub lens" instead of "party lens")

Haven't used the 28mm F1.8 but the 30mm F1.4 is a fantastic piece of EF-S Glass for the Canons.

I still bring it out to night events on my old 350D

Sorry, not really what you asked but in general, I'd recommend the sigma stuff (i also have a 12-24mm & 70-200mm that I love)

I have never used it, but it's also not something I would buy.

I have plenty of other lenses that cover that focal length. The only need I have for f/1.8 is for portraits and I think that 28mm is too wide for that purpose most of the time, even on a crop sensor camera.

This lens is also way too wide to be a useful Macro lens (although Sigma tends to add that designation to any lens that has close focusing ability regardless of whether it is actually capable of shooting 1:1 macro images).

Maybe somebody would have a good use for this lens, but I just can't see it for myself.

I've had no experience with the lens in question, however I have heard good things about the 30 mm 1.4.

As for the party / pub lens idea? If you like the 50 mm, and want a little wider for low light / indoor shots then you should be happy with a 28-30 mm lens.

I often use my Nikon 35 1.8 for exactly that purpose and have been very happy with it. It's especially good with a flash bounced off the ceiling.

Make sure you test out the lens in a shop though just to make sure.