Excuse the noob question, but what benefit do I get from doing this? My last phone (and first Android) was an unlocked Galaxy Nexus. I never strayed from stock Android, since it got quick updates to new versions and I could tether without mucking with it.
There's lots of useful reasons for rooting, even for a stock android device. Unlocking the bootloader and installing a rom is a whole other story though.
I had a unlocked galaxy nexus too and it sucked without the help of custom roms.
Stock android is very vanilla that needs a lil bit of tweaking to make it better.
for example, no percentage indicator on the battery, no notification toggles, no power options, etc..custom roms adds those functionality integrating them, so you don't need an app.
Some roms can also improve the performance and battery life drastically.
and there are time that a firmware will leak and the developers can use that as a base...so you're getting the latest and greatest firmware even months before its official release.
And apps provide that functionality so you don't need a rom.
Most roms also reduce the performance and battery life drastically while breaking stock features.
And that's before rom developers start messing with the leaked firmwares so you can get the latest and greatest betas before it's ready for mainstream use