I use FC and LC brass for my AR-15 in .223 Remington.
I've never encountered any issues with the FC brass. I've heard (but can't confirm) that the FC may not be able to load as many times as LC brass. I've not run into this issue since I don't have enough reloads on my brass to have encountered the issue.
Some people seem to have issue with them and sell them for a much lower price then LC brass. I will definitely buy it and use it.