As stated the biggest pro is that you can absolutely make the phone exactly the way you want it - no blur, no bloatware, rum roms, use apps that require root (Titanium Backup, etc.), modify the notification bar (battery icons, battery single digit meters, etc.).
The biggest con is that you may make a modification (usually deleting system apks, instead of renaming or moving or freezing) and really borking your phone. However, since the implementation of One-Click Fastboot Restore system (
One-Click Fastboot Restore to recover from bootloop or softbrick - xda-developers ), recovery is now a pretty simply matter.
If you decide to do it, read everything you can find and then read some more. You need to understand these processes. Read all you can find about 1) Rooting, 2) Bootstrapper, 3) Clockwork, 4) Making frequent backups with Clockwork, 5) Removing bloat, 6) roms and other system modifications.
That's all I can think of right now (it's early and my brain hurts). Good luck.
