Went here on Saturday afternoon, Memorial Day weekend.
The gardens around the Japan House were very nice. (The Japan House itself was closed.)
The Idea Garden struck us as kind of slapdash. A lot of plants crammed into a fairly small space. Looking at the tags for many of the plants, we could have just visited the garden center of our local Lowe's or Home Depot.
Walked over to the Miles C Hartley Selection Garden, and the selection was somewhat, ah, lacking. A whole lot of empty ground, at a time when you wouldn't expect that to be the case.
We've been to a fair number of arboreta and gardens around the country. This one was, unfortunately, far removed from the best we've seen.