Very nice place to get away for a little while. It's big for a garden, but still pretty small and takes about 10 minutes to walk around. Of course you should stop and feed the fish, and sit and relax on one of the shaded benches. The have a tea ceremony every now and again, which could be fun to check out sometime.
A few side notes, I have been to Japan and to many gardens over there and this is pretty close to what I remember seeing but the scale seemed to big.
Also I know quite a lot about plants (Hello! Botany degree here with 10 years landscape experience) and the garden could use a better variety of plants and filling in the missing plants.