Here's a very early demo of a game engine I'm working on with lots of transparency used:http://www.mycgiserver.com/~movegaga/gldemo1.jnlp
(it's now a windows only web start app using lwjgl).
Now, if you look carefully, you'll notice that although every polygon (well, only quads atm) is depth-sorted (by hand), it still isn't enough: You'll see dark squares around the bouncing stars every now and then (when it occludes the far end of a wall quad). I guess I must even sort per vertex or something? Because in the cases the black blocks appear, the origins are well sorted, but the star should still be drawn after the wall it occludes even though the origin of the wall is closer. (hope I'm still making sense here)...
BTW If the wall is solid and not transparent, everything looks fine.
Or... is there a method of blending that doesn't have this side effects?
(now doing gl.blendFunc(GL.SRC_ALPHA, GL.ONE); )