Hi Warrick
to IIS!
A 9mm is better because the higher magnification will reveal drift sooner - but there's no problem in barlowing the 12mm either. I use a 3x barlow with my illuminated reticle.
The star can end up quite dim, so you need a bright star, but it works fine.
I'm quite sure mine was around $100 from Bintel, but it was on sale at IISAC2007. I'm not sure what the new price is.
I used to remember what PL/MA meant but now I can't! But don't leave the power on - it'll run out of batteries quick, then you've gotta spend another $12 to replace them!
Oh and get one that's battery powered, it's much easier.