- Poor Browser Support. You can make nice prints with Chrome, but Firefox doesn't respect CSS print margins and if you're not careful the map can easily bleed over into a second page. IE prints the URL and title at the top of the page, with no way for the user to turn them off.
- Low Resolution. On my computer at least, setting the map size in inches gives you a print resolution of only 100ppi.
- Fixed Scales. There are a limited number of zoom levels available, and the scale doubles with each one. Often zoom 14 is too broad and 15 is too narrow; there's also no way to print a 1:24K map.
In response to these issues, CalTopo now offers server-side PDF generation. Pick your layers, draw a rectangle on the screen, and hit print. You'll get back a high resolution PDF that will print exactly as it looks, no muss, no fuss.
At this time, PDF generation can only be used to print CalTopo's base layers. It can't be used to print Google's layers or maps from other sources. It also won't show waypoints and tracks from saved maps, although I hope to add this at some point in the near future.
Try it by going to http://caltopo.com/print.html, or by clicking on the "printable PDFs" link inside the standard map page's print mode. Please note that this will become a paid feature in early 2013, but is free for now while I finish development.