I've dealt with Banfield at both the Germantown and Gaithersburg locations. The complaints above regarding the yearly Wellness contracts are based on wrong assumptions.
There is no "month to month" plan. The (optimum) wellness plans are a specific cost for one year, and the payments can be spread out in monthly installments over the course of a year. This monthly installment option is convenient, and from what I recall there are no extra fees for doing this.
When someone signs up for a year-long plan such as one of the wellness plans, there's a risk that something may come up during that year where you don't need the plan anymore. Well, in such a case, you can't just cancel the contract - you still owe the inital plan's cost.
I've had great cost-savings by being on the optimum wellness plan the past year and a half or so (keep in mind, the plan will automaticall renew after the first year unless you cancel it, or tell them not to automatically renew it). I also like Dr. Parma in Gaithersburg, who's very knowledgable and explains things very well, and even finds ways to keep extra costs to a minimum when I've asked. This has not been true of any other vets I've had for my dog (which have included a few other places in the area). In fact, one visit to other vets has easily cost the yearly fee for the optimum wellness plan! Also, the vet techs at this Banfield are very nice and helpful, and also know a lot about dogs (and always remember my dog's name!).
Of course, serious problems do need to go to better equipped animal hospitals, and Banfield will definitely recommend this. For example, when my dog was young, she had a serious problem which was immediately diagnosed as her having ingeseted rat poison. In this case, I was referred to a pet hospital in Rockville, where they could do a blood transfusion (there are not many, or any, regular vet practices that are equipped to do this procedure).
I do recommend Banfield and their optimum wellness plan.