Turns out I was a few years too late. The site is now derelict, with a 'no trespassing' sign by the entrance where you pull off the highway. Had there simply been the closed sign, I wd have been tempted to poke around a bit to see the trail (after all, when was I going to have another chance?), but accompanied as I was by my conscience, I refrained. Still, you can see enough to get a sense of what it's like without entering the site.
From what I assume to have been the parking lot you can see Gandalf standing by the door of Bag End (half the door is missing), two other hobbit-hole's round doors, and the three trolls -- at least one of them v. obviously based on the Rankin-Bass cartoon. Checking google, I see that several folks have posted pictures of the displays we didn't get to see (out of sight up the hill, I assume): Bilbo, a warg trying to climb a tree, spiders and cocooned dwarves, Gollum in his cave, an Eagle, Smaug, Bard and the thrush -- several among them obviously taken from the Rankin-Bass-- and, rather puzzlingly, what looks like Bakshi's Aragorn. In person, it looks more like a miniature golf course than anything, except without as much dignity. No one will really miss it now it's gone, but still I'm sorry not to have seen it in all its awfulness. Let's hope no one ever builds another.
current reading: THE PTEROSAURS.
current writing: "Inside Literature" (Kalamazoo paper)
*thanks, David, for letting me know beforehand that it was in the area
Thanks to all those lucky visitors (David, Monte, Ed) who posted in the comments memories of visiting the spot before it closed. David also published a post about it on his own blog, which is well worth checking out if you haven't already (http://calimac.livejournal.com/437865.html).
One thing I overlooked until reminded of it by some links within links is that the place is featured in RINGERS: LORD OF THE FANS, the Dominic Monaghan-narrated documentary about Tolkien fandom. If you have this dvd from 2005, check out scene 10, which devotes two and a half minutes to touring the place and briefly giving a little of its history (apparently it opened in 1981; from other indications it went into decline after the woman who created it died in 1996). Described as "a living diorama of THE HOBBIT", which seems fair enough, it includes shots of Bilbo and Gandalf at the doorstep of Bag End, someone (a dwarf I assume) treed by a warg, wrapped-up dwarves hanging above Bilbo as he battles a Spider, an Eagle rescue, a castle (?? is this supposed to be Rivendell?), Lake Town*, Gollum's Cave, and the Shire Map. We also get to hear a little of the recorded push-the-button dialogue, which doesn't sound nearly as bad as I'd been expecting (one reviewer said it was obviously recorded by someone who played D&D a lot, as if this were a bad thing).
*"it's only a model!" (by far the cheesiest of all the displays shown -- and yet another internet link featured the company that built the little 'lake' describing how it was done to show the versatility of their product)