First, you should be aware that Magnus has entirely redone its menu and is now a Scandinavian restaurant. So, many of the earlier reviews might not be relevant anymore.
The restaurant itself is beautiful. I think it's easily among the best designed in town.
I've been here many times but only twice since the Scandinavian menu change. I was surprised to see in other reviews that people have gotten food poisoning here. I did too from tuna, which is why I never ordered fish here again (until the menu change -- what's a Scandinavian restaurant without fish?!).
So, commenting on the restaurant it its current instantiation, the food is okay. For any NY'ers reading this, it's no Aquavit. I'd skip the gravlax, which was completely bland. I enjoyed the herring, but it's hard to screw that up. The over-cooked salmon unfortunately didn't have any authentic Swedish influences but the venison carpaccio was interesting (no idea how a carpaccio fits into a Scandinavian themed restaurant).
I suppose I prefer the old menu, even though Swedish is among my favorite cuisines. However, the execution is sufficiently lacking that I'm not sure redesigning the menu was a great idea. I'll likely give it one more try; perhaps they need some time to "grow" into their new menu.