I guess it depends on who is trying to break in and why.

I remember reading a reddit AMA from a former burglar and he said that these windows did stop him, because he would be looking to get in and out as quickly and inconspicuously as possible and these would slow him down enough that he would try elsewhere instead.

So, for a random opportunistic burglar, they may work quite well, but for somebody determined or someone with more time (eg if you live in a secluded area and they know you're away for long enough), there's always a way in. I've watched enough lockpicking videos to know its not that hard and enough defcon talks to know that lockpicking is rarely necessary. If someone determined wants to get into your home, they will.

Exactly - it’s the old joke about not having to run faster than a bear in the woods - just faster than the slowest membe of your party :)

Deviant Ollam has some great talks on physical pentesting and simple, affordable solutions to common attacks. You can find them on YouTube.

Even the walls of most houses are fairly easy to get through.