I've felt for a long time that there needed to be a place on 21st ave that filled the "just right" gap. North 45 is a welcome addition to the neighborhood and fits nicely between the SLOW and inattentive service at Blue Moon, the dive-esque bar-scene of Muu Muu's & 21st Ave Bar & Grill (I love both of those places), the suburban vibe at the Gypsy, and the too-expensive restaurants that line the rest of the street.
The food at N45 is a cut-above the rest of the bars in the neighborhood, the wall of liquor dwarfs most other establishments, and the eclectic mix of beers is just right.
The place gets a little busy, but the new outdoor patio is HUGE and should alleviate some crowding.
I've had such a good time here that a couple of excellent happy hours that have kept me around until closing time. I keep bringing friends here and then running into them the following weekend because they come back on their own.
If you hang out in NW a lot, do yourself a favor and step into North 45 to give it a try.