Not sure which option to choose between "I DM 4e and I use 4e's 5-alignment system or something close" and "I DM 4e and I don't have alignments as a game mechanic", as the 5-alignment system doesn't really have much in the way of game mechanics.
Off the top of my head, I can't think of any mechanical impact it has at all. I dimly recall there being an item or two with alignment restrictions, or an artifact whose concordance was modified based on alignment, but nothing much beyond that. Those items might not even exist, I could be misremembering.
I don't mind them being in there the way they are, as general descriptors with no significant mechanical effects. I also wouldn't be inconvenienced much if they left them out.
I don't recall ever formally discussing alignment with my players. If I did, it was a couple years ago, back when the campaign began. It hasn't come up since.
When I make a character to play, I generally write down "unaligned" on the Alignment line, just in case the DM decides to care. Then I go about playing the character pretty much the same way I'd play them if there wasn't a space for alignment on the sheet at all.