We have used mail away pharmacies for over 20 yrs. Long before the service became common for others.

The plan my husband has started with National RX Services in Tampa Florida back then. Only Medco has been a hassle.
Caremark when we had their mail in service was the fastest in response. I only get a small number thru the mail. I use local pharmacies for my generics typically. Now with the $4 per month offered by Kroger, Target and WalMart, one of my blood pressure drugs is $2.95 for a 3 month RX. That is because the U and C for 90 days for them is $10 on most generics.

But I do get my brand name things, mostly now just my Lidoderm patches from the mail in. Cardizem CD is not on the generic lists locally for the savings, so I am forced to get it from mail away also...but it is now free with the 4 free generic offer Medco is using.

Basically the plans keep changing, they move drugs to new "tiers" so they can charge more, and often require prior authorization for many items. My husband's psoriasis cream requires prior auth. It is just a major hassle, and it keeps changing so every year one has to perhaps go thru new hoops to get certain medications.

MS patients who use expensive biologicals, would have to research the drug plans very carefully, and even then, next year the rules may change AGAIN!