The end result is almost always worth it, especially for older or lower end devices where you can get more performance or battery life out of them.
For example, I've been running CyanogenMod 7 on my 2010 HTC Incredible for years now because it's quite a bit faster, and more stable than the stock ROM, plus lacks the VZW bloat and Sense skin (which isn't that bad on Android 2.1-2.3). Plus where support for this phone ended at Android 2.3, we have custom ROMs taking it all the way to Kit Kat! It shipped with 2.1 Eclair! It had a great community back in the day. Plus a lot of ported HTC Evo ROMs.
Same went with my GSIII I had for a while, de-bloated ROMS, AOSP, better kernels, full backups to SD, you name it.
Plus, it can be a lot of fun and it's always great to learn something new, or learn about how your device really works at it's core, reading up on kernel governors, modules, etc is actually interesting to me.
Can't wait to get my Nexus 5X today, coming from a line of non-rootable devices like the later model One M8 (went through three of those suckers), Moto X 2014 (VZW), and a number of iPhones.