Today (tied in with an appearance by CEO Daniel Ek at LeWeb 2011) that's been upgraded, as the freshest preview builds move the Radio section down among the new Spotify Apps, where it now lets you drop in any song from your library for it to automatically create a radio station of similar music around.
If you really like one effect and you want it applied to all of your photos, a drop-down menu lets you choose it for automatic post processing, instantly applying, say, the color-saturated "More Cowbell" effect to each shot.