On my last visit to Cape Town, I sat down at Arnold's on the outside terrace, because the place was quite busy and it looked like mostly locals where there enjoying a drink or two. I ended up having dinner there as well (spagetti, very tasty).
The next evening, I went back, only for a drink, and the two member of the staff who were also here the evening before, both recognised me, welcome back and the likes, I felt like I had been a return guest to Arnold's for a long time, and that was very nice. I love people watching, and Arnold's seems to get a lot of locals, a lot of them friends / regulars.
Foodwise, it seems that game is "the thing" to order here (which is not my cup of tea), so cant comment on that. Overall, I really enjoyed the vibe at Arnold's, feeling a bit like a local, not so much as a tourist, and on my next trip to Cape Town I will certainly be back there.