Watch the 30 Rock & Pop Progressions online guitar lesson by Ravi from Guitar Lab: 30 Rock & Pop Progressions
As you can see, the craft of songwriting relies on some very stable concepts and proven harmonic techniques. I don't believe this makes anyone less creative, but on the contrary, forces artists to be more creative given the relatively limited amount of harmony that they have to work with, there are only twelve notes after all!
You now have a much better sense of how songs are structured, which will help you learn songs by ear, even without an instrument in your hands. I sometimes learn songs from recordings while driving to the gig!
Plus, if you want to write songs or already do, you can now start with a foundation that hit songwriters have used over and over, and over and over! The guitar is a superb songwriting instrument. You can write in all twelve keys, but several ones have some very unique sounding characteristics, expanding the colors on your palette (piano players don't have that luxury!). The combination of open and fretted strings adds variety. So, even the same chord progression can be played several times in the same key, but still with different nuances thanks to the design of the instrument.
Good luck, and have fun with all this new knowledge!