I've used Dunlop Straploks for years and they are definitely worth the investment. 37,- EUR to make sure your expensive guitar never accidently falls because the strap lets loose? Now THAT's insurance worth buying.
They're pretty easy to install ... except for that goddamned 3/4 ring thingy you have to force in between the lock and your strap. They're a nuisance to install because of the tension involved and the small size of the open ring.
Otherwise they work great — a little oil now and then, I've never had one fail on me. They're great to quickly switch straps between guitars, or to take a strap off if you have to put the guitar in a tight case or gig bag (my Les Paul can't fit inside my Mono gig bag without taking the strap off).
Plus, contrary to Schallers, these still let you put a strap without loks over them in a pinch.
That said, this 'gold' straplok disappointed me. I was looking for a gold version to match the gold hardware on a new PRS I have. However in real life the gold is VERY dull — Thomann's pictures are not accurate unfortunately. For this reason I'm returning them and going with Schallers. Yes, I care about looks. It's why I ordered the gold ones.