Toproping, absolutely. Use you own quickdraws. But lowering off? These anchors are designed for precisely that. If they're worn, they need replacing. If they wear super quickly due to traffic, consider more approriate anchors. Lee (from safercliffs.org)
Lee, lowering off vs. rap, lower off the anchors, all the dirt in your rope cuts like saw. Save the anchor and wear and tear on your rope and the anchors will last much longer, rap off. Some people are TOO lazy.
Gotta go with Lee here. The anchors shown here are specifically designed to be lowered off of - not rappeled from. Why else do you think there is a gate on the top? As Lee notes, if they wear super quickly due to traffic, consider other anchors (i.e. quicklinks/chain).
Also, considering Lee signed his comment "from safercliffs.org" - a little research shows that "Safer Cliffs Australia is a non-profit voluntary organization of climbers who maintain the safety of rock climbing areas in Australia". I would say he is far from being part of the problem....
Edited to add: Regarding these anchors though - I do think a design flaw on Fixe's part was to design these anchors to be lowered off - but not design them to be more easily replaced. The hooks shown here though are an improvement over a style (also Fixe) that I saw in Owens River where the hook was connected to a welded ring requiring the whole setup to need to be replaced. See here www.mountainproject.com/v/california/sierra_eastside/bishop_>>>
I think it's totally fine to toprope or lower from these things - as long as YOU are the one that will replace the anchors when they are worn - long before they get to this point. If not, just rappel - it's actually really easy and safe, there isn't a good reason not to. We can't forget that people die doing this sport.
Yes, rap off anchors. The problem with lowering and toproping off anchors should be obvious from the picture irregardless of what you think they were designed for. There is no one who carries the responsibility to replace these anchors even when they "should be replaced". They only get replaced out of the goodness of someone's heart. So, have a heart and don't abuse the anchors, and they will last longer.