Bryce 6 is worth it, but if you plan on using Metaballs, forget it. It always crashes as soon as I add a second metaball to a scene.
Biggest advantage is the use of HDRI in your renders, a big plus if you're after realism.
When you think about what you'd pay for other likewise software, $20 is nothing.
Bryce 7 will not be around for at least a couple more years, if there is a 7 that is. Looks to me like Daz3D have lost interest in it.