Once upon a time I was asked a question on this blog about low res MFA programs. And I honestly had very little to say that you can't find elsewhere. Not that this helps overmuch, but you can read this blog post over on the emerging writers website written as the day account of a resent panelist at a low residency MFA and his take on what he saw there.
Basically (and this is the take that you can find anywhere else on the web) the low residency MFA is for people who want to get an MFA but cannot relocate to a new city because of job or family obligations. It is also a good program for people who do not want to use their MFA to write not to gain a college teaching position. It's great for writers who have a day job, want to keep the day job and enrich their lives through further study of writing.
In no way would I say that low-residency MFAs are lesser programs. Some of them are harder to get into than regular residency programs. It's not like going to "night school." It's an intense process and you have to be dedicated to it or you'll never get better. But it is a nod to the fact that many writers never earn a living off of their writing. And because of that you'll hear many people tell you not to apply to campus based full-time MFA programs unless you want to teach.