It's just that writing a compiler requires such a large up front amount of knowledge of how computers work, and teaches you so much more, that it's hard to comp

It's just that writing a compiler requires such a large up front amount of knowledge of how computers work, and teaches you so much more, that it's hard to compare to any other project where you can learn exactly what is happening in a computer and what every line of your code actually does to the operation of the machine you are working on/targeting. Sure other projects you can learn just as much general knowledge, but I'm going to agree with Steve that it's pretty enlightening. I'll also agree that it is a bottomless pit of your time and effort.