Sam Smith pubs are always a bit of a mystery to me. The mystery isn't why people go to them, the mystery is why the whole world doesn't. Perhaps people turn their nose up at a pint that costs half what you pay elsewhere, but Sam Smith pubs serve a broad range of decent beer and are typically in nice historic buildings (think, notably, The Princess Louise and Cittie of York), so it isn't like selling your soul to Weatherspoon's for a cheap pint combo with a burnt gristle disk masquerading as a burger.
The Fitzroy is not my favorite of the Sam Smith pubs, but then there's nothing huge to complain about either. I'm not fond of the pen they try to keep you in next to the building (in effort to keep the path clear for passersby, fair enough): it makes you feel like a pig in a poke, although it's more like a media mosh pit. It wouldn't be half as bad if the wankers around you didn't look at you like you spat on their mothers' graves when you try to squeeze out to find another drink (they were probably worried I would scuff their designer trainers, or momentarily prevent them from being seen by others). Not the place I would go to chat with strangers, but not a bad choice in the neighborhood for a cheap pint.