It depends what your goal is. Linux from scratch will mainly teach you (wait for it) how to build linux from scratch. Systems that are not quite "from scratch" but are lower level than Ubuntu (eg, Gentoo, Arch (others?)) will also teach you some of this. I used Gentoo for years, and after compiling about a dozen kernels in a row to get things to work how I wanted, I guess you could say I'd learned something, if only 'what kernel options I want to enable on this hardware'. :)
But building Linux won't really teach you to _use_ it. If you want to be a power user in the long run, your time (and LFS will take a _lot_ of time!) might be better spent learning your shell/package manager/scripting language of choice in greater depth, compiling your own kernels and adding them as options in grub/lifo, that sort of thing.
All that said, if the LFS process sounds really appealing to you, go for it. You'll definitely learn _something_, but just maybe not as much as you're hoping.