Kelly's is one of my favorite places to go when the patio is open during the summer. When I am forced inside by the weather I still stop by occasionally but it is not nearly as fun. Inside is a bit to dark and loud for my taste.
The drinks and food are both very good. I do love the mac and cheese; it is exceptional. Everything else on the menu is solidly above average bar food. The drink menu is all $6 and is all retro cocktail style drinks. I have had a mixed experience going off the beaten path on the drink menu. I usually stick to a Manhattan (they make a pretty good one). The beer selection is quite good too. Usually they have 8 or so micros on tap plus a pretty solid bottle list.
The service can be a bit hit or miss. As longs as you are willing to hang out for a bit you will be fine, but I have ended up sitting for a long time waiting to get my drink. Usually they have two waitresses for the whole bar, which is not enough, so it is understandable.
Summary: Go check it out during the summer and hang out on the patio. Get the mac and cheese.