You can download ready-to-go map data for CD-OS from OpenMapTiles.org in MBTiles format. I use Melbourne but you can use and attach anything you want. You put it into the GEO directory and include your path to it in the configuration file, it will be attached at startup to the main database.
This is a vector tile, very low bandwidth! I was drawing those tiles myself and sending them downwind as PNG files with Cache-Control and ETag set to never expire in the browser cache.
Then I discovered this! A plug-in for Leaflet that takes delivery of the tiles in their original vector format and draws them using canvas. Incredibly, I tested this with excanvas (Explorer Canvas polyfill for older IE browsers) and it worked!!!
My map server may be cheating and it may also be doing some optimizations for smaller regions but the CD-OS map server blows Google away in speed! No lag and no delays after I cleared my browser cache and started from scratch. I compared scrolling around Melbourne in Google to scrolling around in my server and no contest. A complete vector tiles file for the entire planet will run you around 50 gigabytes at present. I would host that one except I don't think that CD-OS would fit on a floppy anymore.