We used to have the dome lids:
Then, probably in order to save a few pennies, we switched to these lids:
I hate them. (They aren't the brand pictured over there, so none of this hate is directed at Dixie) The lids are terrible. You are supposed to peel back the tab and lock the little nub into the divot. A divot that has only a passing resemblance to the nub. I have gotten poked in the septum on more than one occasion. Not really one for the "fun" column.
Not only is there the locking issue, but the edges created when you peel back the tab are lethal. I don't have a particularly full lower lip and I still feel like I'm going to have hash marks. Bloody hash marks on my lips. And no, I can't just remove the lid because we aren't allowed to have open containers at our desks. Knowing my luck, I'd take the lid off to get a sip and promptly dump scalding hot coffee all over the place.