TileMill is great, I used it to style our replacement maps, since google maps decided to start charging. Here is an example: http://tile.ridewithgps.com/leaflet.html
TileMill is addictive to play with, though very tedious if you don't have a fast machine with some SSD's, as refreshes take a while to reload various zoom levels to see your work. Not much to be done there except throw hardware it.
Edit: I am hosting our maps on my own hardware, mapnik2+mod_tile. I just used the slick client to create a mapnik XML file for rendering.
Your demo displays one problem : the strange choice of labels. For example, look for France's capital at zoom 8. You'll see a lot of small towns indicated but not Paris. And I can reproduce this for a lot of notable towns (like NY).
He must be sorting the labels in reverse order of importance. I notice that if I zoom in near Chicago, Chicago itself is missing, big suburbs are in the smallest font, and small suburbs are in a big font. Looks like the data is right but the sort order is wrong.
I am constantly tweaking at label sizes, and which labels to show at various zoom levels, and am not quite satisfied. You've pointed out an issue that is on my todo list. Problem is, it's easy to get sucked into a full day of TileMill styling, and I have to get some other stuff done over the next month ;)
I just haven't taken the time to fully dial in the details available at each zoom. It's really hard, since in one area that level of detail will look sparse (much of the US), but in the UK, that much detail at a particular zoom will look way overcrowded. It's doable, but takes alot of patience and tweaking, which is my next round of styling. That and US state borders being messed up.
Question: where did get the map and terrain data from if I may know? I used shapefiles from OpenStreetMap but they aren't as complete as I thought they are.
Map data is a complete OSM planet import - 20gb compressed file, expanded/indexed into a 225gb database. OSM has lots of good data but most custom styled maps leave out a good amount of it, or, in the case of the OSM style maps, they include way too much.
Importing and indexing planet.osm takes a while. It's better than importing the whole planet file in gazetteer mode for geocoding though. I have been fighting that import for a month now, on decent hardware!
possibly inappropriate but i'd just like to say that i'm a huge fan of ridewithgps, best by some way for planning/sharing routes (i have never actually used the gps bit)
TileMill is addictive to play with, though very tedious if you don't have a fast machine with some SSD's, as refreshes take a while to reload various zoom levels to see your work. Not much to be done there except throw hardware it.
Edit: I am hosting our maps on my own hardware, mapnik2+mod_tile. I just used the slick client to create a mapnik XML file for rendering.