This comes back to what many of us have said before -- it's great if you have a meter and can do your own testing. This way, if you add or remove a medication, or make other changes, you can test more frequently and detect any changes in your INR BEFORE these changes can become serious problems. (And if you detect an abnormal INR, you can get help more quickly).
Personally, I believe that anyone taking Warfarin who is able to successfully test his or her own INR SHOULD be able to do self-testing. Meters and supplies should be affordable -- and if the number of users gets to where it SHOULD be, the supplies and meters SHOULD become much more affordable. (And for those who either can't afford testing or aren't capable of self-testing, the tests should be affordable (or even free), and test locations should be convenient and easy to find).