LFS is great to learn how a Linux based system works without all the sweet, sweet magic modern distributions give us.
On a personal, nostalgic, note: running LFS on your laptop in my university was the ultimate Linux nerd cred. A step below, immediately following, there was Slackware.
The reason I feel confident enough working with Linux today is because I started back in the early '00 using Slackware, which recently had a new release[1].
Don't get me wrong, compiling your own kernel, solving shared libraries compilation hell, messing up your init.d and starting over, leaving your Pentium 4 compile for several hours was a massive waste of my 20s. But, boy, did I enjoy it!