Comment 4 for bug 696431

If you see the fading background on shutdown, it means that the script is run. In the current implementation the script tells the splash that the machine is shutting down (there must be a better way to do it, but I haven't found it yet). There's a mysterious limitation in Plymouth script engine that doesn't let me start text animation before the background animation is finished, I guess your machine shuts down faster than the background fades out to 0.5 transparency. The limitation absolutely mystic and illogical, so probably it's just me. I'm going to investigate it.
Regarding the boot time, I tried to fix to this bug, try version 0.3.2 from the PPA (it will arrive in a few minutes).