D's quite possibly has the best beer selection in Pittsburgh. There are always 20 micro brews on tap and they rotate seasonally. Last time I went they had a variety of pumpkin beers and I pretty much tried them all to figure out which I liked best. If you aren't feeling any of the beers on tap then take a stroll to the walk in cooler in the back and take your pick of hundreds of bottles. Bring the one you like back to the bar and the bartender will open it for you and bring you a glass.
The bartenders are really chill, and though the service isn't overly attentive, it is perfect for the vibe of D's. And speaking of the vibe, D's has this old pub style feel with the walls meeting at strange angles making cool little nooks and crannies where you can sit and sip your beer with friends or maybe just read a book.
D's is also known for their hot dogs, and while good and inventive, in my opinion are a little overpriced. For some reason I have trouble spending $5 for a hot dog. I've tried their wings and fries too, both good standard bar food, but again a tad overpriced. My friend and I drank beers (a good amount) and ordered food and our tab was $100.
D's still remains the gem of Regent Square and is worth the pilgrimage to Beer Mecca if you have never been.