Mary, sorry for the late response...
We've converted all of our code from Proc LP to OptModel... in about a week. It was rather painless. The transition was much smoother than I expected. (converting from ILOG OPL 3.5 to 4 was hell!) The best part was that the entire exercise was transpartent to our downstream folks.
We had some advantages however, we've experience with AMPL/OPL/CPLEX so the 'new' SAS/OR language came naturally for us.
At any rate, our model is responsible for over 3000+ branches and 7000+ ATMs. A simple mutli-staged inventory network... 2 billion+ hard currency is being churned by SAS everyday...