Today we actually used this thing briefly during an Ovid/Medline training class, and although many drawbacks were quite apparent, it seems to show real promise in fulfilling its main objective. The main drawback during the course was that it was only used for the MeSH part of the training session, after which the actual Ovid interface was used (with its own MeSH mapper and browser), so that might have confused folks. Hard to know, but it seemed jarring to go from one modality to the other.
There are _many_ things it does not yet do, foremost among them any type of proper term mapping for synonyms, obsolete terms, stemming, etc. We'll probably add those things in soon because they're not too hard, and it's not too useful without it (you have to type in terms exactly right now). There are some yawning UI gaps (like a proper scroll-and-zoom arrowset like on map sites) to address. There are also many features we'd like to add, but we're going to focus on improving it according to the teaching objective, and when we've gotten far enough along maybe we'll look for some dedicated development funds to take on some bigger objectives.
In the meantime, though, it's already pretty fun to play with (remember when "stickiness" was important on a web site? this is way sticky, especially if you care about MeSH or Medline at all...). It's on a development machine for which I can't guarantee uptime, but so far it's pretty reliably available, so if a few of you hit it concurrently it shouldn't explode. Some of the relevant code is linked from the technical discussion page, but it's nowhere near any sort of release quality, so feel free to borrow ideas, but not the code (yet!).
Sigh... this is the hard part. If you want to play with it, you'll have to (gulp!) install Adobe's SVG Viewer and run it from IE on a modern win* machine. I know, I know, it's just that there are _no_ reliably useable alternative SVG viewer implementations available yet, so this is the only option. Trust me, I'm watching the alternatives (moz, batik, kde, corel, etc.), and not a single non-proprietary version is useful enough to see this app yet, so we're developing to the adobe+ie "standard", even though that's already 18 months old.
Anyway, have a look, and tell me what you think, it's here.
url, server, etc., all subject to change, and keep in mind, it's alpha quality! :)