This is a very hyped-up area in Oslo. It promises to be this place to hang out in cools cafes,…read morebars, and restaurants. I guess its interesting but it all seems just a little too much contrived.
Basically, Grünerløkka is this one very long street. Yes, there are tons of places where you can grab a drink or a meal. And yes, in the evening this place can get pretty full of both the local crowd and the, "Looking for something Oslo-ish," travelers. So, it serves its purpose. But, it's just really not that much fun. Some of the bars get way too crowded awhile others are just empty and looking for customers. That's the paradox of this area.
This street does have few shops that are pretty interesting. So, it is worth the visit. Just don't have too high of expectations. I'm not saying anything negative about this area, you just need to know what to expect.