I was excited to try these out, from what I'd heard they are the best. I had read other reviews saying that the installation was difficult, however our only problem was that because our cupboards have a little silicon bumper pad in the corner, the foam on the sticky installation guide wasn't thick enought to hit the cupboard...we just doubled two of them up and it was fine.
As for the function of these locks...they are awesome! The traditional cabinet locks allow you to open them a finger width in order to push down the plastic piece to open them all the way...with Tot Lok you can't open the cupboard even a little bit, which eliminates any finger smashing for your little one. Admittedly, it was a hard habit to get into, using the key every time...however I soon got the hang of remembering to grab it, and I also make great use of the "permanent unlock" bar, which you can flip to keep the cabinet unlocked if you like. This way, if I am cleaning up and need to throw paper towels, old toast, leftovers, etc into the garbage under the sink, I can just keep that cupboard unlocked while I'm doing my thing.
These loks are completely invisible on the outside, and not bad looking on the inside. The hardest part was introducing our new cherry cabinets to the drill bit!
I would buy these again and again and recommend them to all parents!