I have no complaints about CVS employees, but the company has policies with regard to controlled substances that show little regard for the patient. They have told me that their supplier rations shipments of controlled substances to each store. So when they reach the monthly quota for that store, they will actually say "we have run out, bla bla..." sometimes they will blame it on the DEA (as if planned Rx shortages are part of the war on drugs). The employees generally try to help, but this is clearly a policy issue.
I actually prefer the small vials though. With 10 ml vials, there is the risk of losing months worth of medication, all from one screw-up (either from loss, breakage, contamination, etc.) I am not sure I understand how drawing from more than one vial into the same syringe would "contaminate" the contents. Yes, there could be some mixing from one vial to the next, but if it is all sterile and all the same medication, what is the concern?