Questioning the UX of an App I've Never Seen

This is an odd one. There's an App out there called Tinder. I've never seen it but have heard a few people talking about it on the radio and on podcasts. Without even seeing it for myself I'm questioning its usability. Is that normal?

From what I understand it's kind of a dating service where the user is shown photos of other users in his/her vicinity. The idea is you then basically accept or reject each and if 2 users accept each other something happens - I don't know what - they didn't talk about that bit. I'd guess some kind of notification or they go through to the next round or, at least, some kind of progress. Anyway, the point here, and the bit these conversations have focused on, is the design of the basic accept or reject user actions. Apparently you swipe left for one and right for the other and users are getting confused. They either forget which is which (I'm sure there are some visual cues so assume they must be going very fast), or they try to go back to a previous one and reject them (I guess that swipe left is probably reject then?).

My immediate thought was why not make the left and right swipe simply the means of navigating between photos and make swiping up and down the reject and accept actions? It seems more logical to me that a swipe up is pushing the photo away - reject - and that a swipe down is pulling it towards you - accept.

There you go. In my head I've redesigned the UX for an App I've never seen.