Yes, I know about the zooming. I even mentioned it in my post. The doubt that I expressed was based on the fact that a tile at a higher zoom level would store information for a smaller area. If you do not want different tiles for different zoom levels, then you have to choose a suitably low zoom level as a base, like a whole country or even bigger. But then you have the opposite problem, too much information in the tile. If you still have to download tiles for different zoom levels (which, if I understand rinigus' post correctly, is the case), then the difference in bandwidth is IMO negligible and hardly worth the extra code the client would have to contain.

The rotation and labeling are good points through, I admit I had missed that.