I have eaten here (Downtown SF location) a number of times because I work nearby. It has a dedicated GF pizza oven and they use a separate counter for prep. But stick to the GF items on the menu. If you customize your pizza (instead of sticking to those marked as GF on the menu) some of the toppings may come from the same line as the regular pizza. Just be clear with your server that your food must be GF and ask questions, especially if you are unsure. The staff are trained RE celiac, but people anywhere can make mistakes, or may not really understand the issues. The wait staff are nice and will return items to the kitchen when they make a mistake.
— Very
— Gluten-free items are marked on the main menu
— Some
— Good