TL;DR - friendly staff with good vegetarian/vegan options and large portions.
We stopped here on a somewhat disastrous trip and this is probably the first place we've been in Pittsburgh so far where I've actually felt like I'm on vacation. Just entering, the decor was lovely and the music was soothing and not too loud (which worked well for me, as I was recovering from a migraine.) The AC was a little cold for my tastes, so you may want to bring sleeves if you're visiting in the summer and get cold easily, but it wasn't absurdly cold.
The service was friendly and attentive, and the menu was packed with vegetarian options. (I did ask and was told the red and green curries did NOT have fish sauce, but do be warned that they are SPICY.) The portions were HUGE (more than either of us could finish in a sitting), reasonably priced and delicious (I had the vegetable skewer and the red curry with tofu, and my mom had the butternut squash coconut soup and the crepe thing.) Definitely recommended for vegetarians/vegans in or visiting Pittsburgh.