Not a bad way to kill some time if you are in the area. The grounds, building, and displays are all very well kept and maintained. The displays are interesting, beautiful and informative. Can be a romantic day date or a fun outing for the family if you time it with many of the kid friendly activities they have at certain times throughout the day.
The gripes (and why not a higher rating). It is not particularly big space. You can walk the entire grounds at a very leisurely pace in about an hour. There is a nice little eatery/snack place on site.
My only other gripe would be the hours. It closes fairly early at 5pm on most days of the week.
All and all a good way to kill some extra time if you are in the area.