The revision that just came out this month is 4.4, KitKat.
They go in alphabetical order - Cupcake, Donut, Eclair, Froyo, Gingerbread, Honeycomb (tablets only), Ice Cream Sandwich (ICS) , Jellybean (JB), KitKat (KK) , ...
Not sure what the update schedule here is yet.
I have a phone that rocks with Gingerbread, another with ICS.
Updates are fun and great but Android has advanced to the point where they're usually just not critical.
Having root is the same exact thing as having admin privileges on your PC. It's great but you're wise to be cautious. Lurk in the rooting threads, make up a list of questions so you're clear. I lurked for a good couple weeks before asking about my first root and was glad I did.
To save data, do you surf much? Check out UC Browser, it'll do cloud acceleration and reduce your data.
Check out 3G Watchdog to see how your data consumption goes.
Get Wifi Analyzer to be sure your home router doesn't have channel conflicts with the neighbors.
EStrongs File Explorer is cool.
CallTrack will store your call history to your Google calendar, but does use some data.
Helium Backup is your friend.