Met my li'l sister here for a sister day and it was pretty perfect.
It's a bit bright for us upstairs as there are windows along three walls but downstairs was a bit more den-like, which I liked.
The staff were lovely and helpful. I am coeliac so I love a lounge (and spend a fair bit of time in them). It's just nice to know I can reliably eat there, although tbh a more interesting dessert selection would be nice. I am also pescatarian and dairy-free (a.k.a. ruddy awkward!) so I am generally just happy when there is something I can eat.
So yeah, it's a lounge, predictable food, predictable (yet eclectic) decor and well trained, helpful staff.
Best enjoyed with a sister (unless your sister is horrible, in which case my commiserations).