Anyone own one of these?  I put one on layaway and will be picking it up fairly soon.  Anything that should be taken care of right away?

Nothing really comes to mind.  My Mk II prefers CCI ammunition the best and Federal the worst.  Several accessories are available but they don't do much for you unless you plan on serious competition.

Also there is an entire forum dedicated to the Ruger .22 pistols at:

Ruger Rimfire Pistols Forum

Edited because I can never get the hyperlink thing to work on the first try!

Just keep an eye on the rear sight pin as they tend to walk out of the hole sometimes. I peen the holes with a punch just enough to keep the pin in place, centered. Get familiar with take down and reassembly for cleaning, being rather unique. That gun will last forever. Mine all like any ammo and I sometimes wait till first malfunction before cleaning. That usually comes way after a brick or so. I think you will love it!