Well first, its going to have a new and improved interface (see quick look video), and second, its going to have many new and improved features (such as being able to export a high resolution Miniature scale maps), but most important is a new payment model. You see, Tiamat is going to be FREE to use. Anyone can login and make maps. Make as many as you want. You'll only have to pay for the maps you want exported for gaming.
In addition to being a map maker, it's also a Map Tile store. And you only have to buy the Tiles you want. No need to buy a full tile set. Just make a map from the nearly 3000 tiles created by Skeleton Keys and just pay for the Tiles you use. Once you buy a tile its yours and you can download the PDF for it anytime. Or make new maps using it and they will be cheaper.
Here's some of the new feature and future plans for the tile mapper.
Future Plans - Mobile interfaces for iPhone and Android users. - Export maps for online gaming tables. - Buy color prints of your maps to be mailed to you.
I'm not 100% done yet, but I'm close to letting people start playing it. In the next week or so, I'm going to let owners of the e-Adventure Tile Mapper have access to make maps (but not export them yet) and get some feedback. Then I'll add the ability to export maps and open it up to the public.
Also, people who purchased the e-Adventure Tile Mapper with received $10 in credit for use in Tiamat. Also, I'm putting the e-Adventure Tile Mapper on sale for $10 starting today. So if you want to participate in the alpha and beta testing, you can, and you'll also get the $10 in credit.