I wish it were more commonplace. I've been in the industry for ten years, and my current employer of two years has been the only shop where there are scheduled code reviews. I think it's great, and I enjoy reviewing other people's code as well.
It can't be checked into source control until it's been reviewed.
There are lots of benefits:
We all have to write readable code.
We can't just put in hacks.
You learn stuff. When reviewing others code you can ask why they did something in a certain way. Sometimes you'll learn about the benefit of coding in a certain way, or using a certain method / style / whatever.
This also has the benefit of redundancy. It means at least two developers know an area of the codebase. So if they're away there are no bottle necks, the other developer can also code that area.