I came here for a casual drink with a friend before and also tried some of their food as takeout. There are two entrances to Walrus from what I can tell - one outdoor entrance on Bay / Wellington and one underground in the PATH on the CIBC side of the tunnel to Brookfield place.
The one time that I went in, it was for a drink on the main floor of Walrus. The ambiance is superior to its peers (i.e. King Taps) and that is what I like the most about the restaurant. It is a bit dimly lit and the music was a bit loud, but that all added to the experience.
I have not tried enough of the food (and enough times) to have a concrete opinion on it, but I believe the pub food here is superior to that of Cactus Club. I have tried the fried chicken bits and they are great - the Pizza is good too!