I've actually been there, went to Japan for a friend's wedding in Tokyo and spent an afternoon around the Omiya area...only thing that kinda sucks you can't take pictures of all the exhibits...only certain ones they allow you to take pictures...then again the website shows all the exhibited ones lol
I spent a day at the Omiya Bonsai Art Museum last week photographing for an upcoming large format art book. The place is fantastic!
A complete history and photos of many of their bonsai (originally the Takagi Bonsai Collection) can be seen in my International BONSAI magazine, 2010/NO. 4 issue. I'm going to try to attach a pdf file of the article. But if you subscribe you can see and read the article with better quality photos.
Bill is right - a fantastic place where very high quality bonsai are displayed and can be viewed by visitors. A must see in Japan for bonsai enthusiasts! And very educational as well - there is an indoor wing displaying the various types of tokonoma displays and other sections with historically significant bonsai books, prints, pots, etc.