Big Dog is definitely the coffee location to choose on the "other side" of the Birmingham Bridge. It's only a short walk across the street from Caribou and Crazy Mocha, and definitely worth the very short trek!
Big Dog has a great space--really pretty/secluded outdoor seating, nice decor, comfy chairs, good outlet options for those with electronics, and a word-burning fireplace. Space-wise, it could easily be one of my favorite Pittsburgh coffee locations. It's usually possible to find a seat, though it does get crowded at key times during the week. Street parking can be a bit tough to find.
The menu options are a little touch and go--love the fresh, local juice options and the amazing oatmeal bar. The variety in their baked goods is nice, but some of the options don't seem like the best local Pittsburgh bakers have to offer (chocolate chip cookies and scones have texture and moisture issues).
They mainly brew Intelligentsia coffee--which is pretty good stuff. They don't have a huge tea selection, but their flavors seem carefully curated (try the distinctive mint iced tea in the summer!).