I don't know what it is about this phone. Maybe the perceived value over my LG G2 since its 1/4 the cost, but for whatever reason I just like using it more. I started out using the 635 for phone needs and the G2 for games and media, but at some point last week I started leaving the G2 at home. the 635 gets better battery life (don't ask me how), gets more attention with the orange and green backs, and has been more useful has a personal assistant thanks to Cortana. Anytime I need to do anything when I get home, leave work, or when I get to the end of a destination, I just tell Cortana to remind me. So far, she's been right on the spot with everything.
I probably will stick with this phone for another generation and see what the 645 or whatever orange phone has to offer.