We went to the Matisse exhibition at the Tate the other day. It's good, not as good as the press seem to think it is. I wouldn't say "Nothing can prepare you for the joyous brilliance". It's worth a visit though.
A friend I went with remarked that while the pictures were nice, you can see them all in Ikea. Which is sort of true.
Also, taking pictures. Come on museums, come on.