Check out "Wheres My Droid"
And there are many others as well.
Getting root is the same exact thing as getting admin access on a PC (Win, Mac or Linux). Unlike jailbreaking, you don't leave the ecosystem for another. Root isn't required to customize your phone and you can do more customizing with a stock HTC than you can a jailbroken iDevice - and then root takes it to the next level. With it you can obtain fundamental changes to Sense or abandon it. (Personally, I like Sense so I go the fundamental changes way.) Visit our rooting forums for more details (under construction/expansion starting today).
Common stock customizations - first, your browser. We have more than I can name. I recommend Boat Browser and strongly believe that it's better than stock by far.
If you'd like to experience a different home screen approach without Blinkfeed, try the Nova Launcher and its wealth of free themes. If you don't like it, uninstall it and you've harmed nothing.
For a better video playback experience, try Dice Player or MX Player. Dice is better but I find it easier to play some audio files with MX, so I use both.
Anyway, just some ideas, nothing that you _need_ to do (but you'll thank me for Boat Browser after you customize it to your tastes).
Welcome to Android and the forums!
PS - I don't have the One yet but I'm a reliable haunt for HTC forums lol.