The by-products of fermentation (proofing) are heat, alcohol, and carbon dioxide, hence the "beery" smell. If over-proofed, you're more likely to see the effects in your bread's structure, which will be poor, causing it to crumble or break apart when you slice it.

Anything with yeast in it can overproof or over-ferment. But this isn't necessarily a bad thing--taste the bread. If you like the flavor, there's no need to worry too much about it. Sometimes, yeast can give breads a beer-like smell.