I've used TileMill pretty extensively, and while TileMill is great for generating static maps (PNGs) for infographics, it won't replace Google Maps any time soon for serving dynamic maps.
For example, you can serve a dynamic map of Washington DC on a website using TileStream and TileMap, but if you wanted to also view Fairfax, VA or Baltimore, MD, you're out of luck unless the tileset includes those tiles. With Google Maps, you always have access to all the tiles.
That's not to say that TileMill isn't a great product. The choice to use CSS is brilliant. Plus they're based in Washington DC, where I'm currently living! Nice to see tech outside of the Bay Area, NYC and Boston.
For example, you can serve a dynamic map of Washington DC on a website using TileStream and TileMap, but if you wanted to also view Fairfax, VA or Baltimore, MD, you're out of luck unless the tileset includes those tiles. With Google Maps, you always have access to all the tiles.
That's not to say that TileMill isn't a great product. The choice to use CSS is brilliant. Plus they're based in Washington DC, where I'm currently living! Nice to see tech outside of the Bay Area, NYC and Boston.