on d4v3's suggestion about Whiskey Sky: neat bar, kind of small (the bar area itself), awesome views. The drinks are expensive, yes, (around $12 for a martini), but that's what you come to expect in that area.
on Kman's suggestion for Redhead Piano Bar: Also an excellent suggestion. This place gets really crowded, best to start earlier, although, I'd use that as a general suggestion anywhere in the RiNo or Rush st area. This place is mostly an older crowd (30's+). The piano music is fun, entertaining.
Despite earlier comment about it being an older crowd, when my friends and I went in there a few years back, we (in our 20's) did not feel out-of-place. We mostly felt the lack of seating, heh.