Bob A.
Yelp
My review encompasses the museum and the restaurant. (There's a "Tate Cafe" entry here on Yelp that is old, I think that's something else.)
St. Ives is super arty, and having a Tate museum in town honors that nicely. But I still get more out of just ducking into the various galleries and studios around the village than I did from my stroll through the Tate. But that's largely because of my taste and my relationship with modern art. I like when art is more playful, art that makes me feel like I'm in on the joke, as opposed to "my lazy paint-roller slappings are important, you wouldn't understand". In that way, this location is a bit less fun than the big one in London. But it's still diverting, and anyone is likely to get at least something out of it. If you have an appetite for modern art and are in St. Ives, you'd likely regret skipping the Tate.
I had lunch in the restaurant, "Sea View Restaurant & Bar". It's kind of swanky, with a small menu of pretty expensive entrees including a £27 steak. I got the £24 seafood curry, Langoustine Moqueca. It was really tasty actually, with its slightly spicy curry broth and a variety of seafood chunks. There lot of cool spots to sit and enjoy views while you dine, including a patio. Upbeat staff, very attentive.
But wow was that an expensive lunch.