yeah, the importance of compressing vocals out front was the impetus for one of the biggest fixes of the 2.0 upgrade! if you want a pro-sounding pop-rock mix you gotta compress the vox at least a little, so quiet singing doesn't disappear while loud singing blows up the room (or your speakers).
its probably the number one use if you only have a single channel of compression.
(4:1 with fast attack and release, set so normal singing gets you just a few dB of reduction, sounds natural to me while keeping the vox just on top of the mix where it belongs.)
the issue with feedback is from compressing monitors, which you don't wanna do.