I am going to go skimmerless soon, my skimmer doesn't hardly skim anything anymore. I have a 50 gallon refugium with about 20 mangroves and lots of grape caluerpa. My water qualities are great and I only do about a 20 gallon water change every 3 months (plus daily kalk+R/O water as make-up). 20 gallons is not much for 180 tank + 50 ref. The only corals I have lost are the ones that were smothered by their sps neighbor. (I know thats pretty lazy I should move them before they are murdered)
I think that skimmers are very useful for new tanks mine worked overtime when I first started my tank. I'm kinda getting tired of looking at the ugly thing though so I'm letting a customer borrow it till her tank becomes established.