It works!
The 315MHz receiver with the RF lib from Thomas works at close range right out of the box.
I did a rough tuning to 310MHz by connecting the data line to the line-in on my soundcard. There's lots of noise, but when you transmit an X10 signal, you can hear it clearly. Moving the transmitter further away while adjusting the slug (start CCW) gave me reception from most of the house and some motion sensors outside.
Nothing left to do but build something with it. Thanks Thomas - great code.
These are antenna lengths (in inches) for a vertical antenna at 310MHz . . .
1/4 wave - 9 1/16"
1/2 wave - 18 1/8"
full wave - 36 1/4"
I've posted a bit more detail on my blog and will post more when I'm further along.