It looks incredibly boring from the outside, because you're not part of the game. The feeling changes the moment you start to play.

The funny thing is, this game makes hanging out with non-players a bit annoying, because you're constantly forced to keep your phone in your pocket by people who don't understand that you can have a productive conversation while hacking a portal at the same time.

Not everyone can multi-task that well. I know at least 2 people, girlfriend included, that can't do anything when on their phone. They'll literally stop in their tracks when walking on the sidewalk or completely drop out of a conversation when reading / writing a text message. Let alone playing a game. I also think its a bit rude to play a game when in the company of someone else trying to have a conversation.

My wife can't multitask - she'll call me when she's walking to relay a two-sentence message because she can't type and walk.

I agree that it's rude to play a game when having a conversation with someone, but it's not rude at all for two people to be walking along and playing the same game.