I have both, but I would never use PW1 as a backup for PW2. Currently I'm using a $69 Kindle and a PW2, I'm pretty comfortable with both now. Personally I find the PW1 significantly worse than the PW2 or the $69 Kindle experience. I'd rather use any of my other e-ink Kindles than the PW1.
The first PW1 is merely for testing out things now, like new updates and PW1 vs. PW2 differences (
http://www.kboards.com/index.php/topic,165383.0.html).