I have been watching this lately, loving it to bits and pieces, and felt compelled to discuss it.
Claire: ESTJ
No doubt about it. I don't see ESFJ as she shows no signs of a dominant Fe and Phil is way more empathetic with his NeFe.
Phil: ENTP
I think he is a clear goofy, awkward, feeling ENTP in all ways apparent. The way he explains (and is an excellent teacher) things is mostly logic derived and the way he tries to Fe but does it in an awkwardly cute way screams a tertiary Fe. ENTP. Also his devotion to his wife, wow.
Hayley: ESTP
Dylan: ISFP
A really, really stupid and weird ISFP.
Alex: INTP or INFP
The know-it-all, misunderstood geek in a house of extroverts. Compentent, dislikes stupidity most of all. A healthy INTP. Or a more learning oriented INFP. My view is very different from the rest of the people here it seems. Why is Alex seen as an ISTJ, can someone elaborate on that?
Luke: ENTP
I'd put Luke in the same boat with his dad. He has the attention span of a goldfish and doesn't care to define things or particularities the way her sister, Alex does. He's also borderline immoral in getting his ways, suggesting NeTi. This as opposed to his sound of morality, Manny, a FiNe.
Gloria: ESFJ
No questions asked. The perfect mother-type.
Jay: ISTP
The dude owns a closet company, what could be more ISTP than that?

He also came out of his shell later in life.
Manny: INFP
The hopeless romantic poet, the definition of a more extraverted, not secluded INFP. He is displayed as an old soul in the series, but I see it more in practical matters, so a stronger Si -> INFP as opposed to INFJ. Also, his dad couldn't be anything other than ENFP.
Mitchell: ISTJ
Lawyer, practical, obsessive-compulsive. ISTJ.
Cam: ESFP
I don't see the fuzz about Cam being an N. Stereotypically, maybe, but that's due to a heavy fall of mistypings IMHO. I see him more as an ESFP with all the weight on details. Very vivid, codependent and no introverted ways whatsoever, wants to be the center of attention, a boisterous ESFP. Then again, not so tidy, as would be expected of an N, but I still stand my ground.
Lily: Funny
No idea yet, her character has just come to life as I'm in the
beginning of the 5th season. She was really, really calm as a child.
Why is Alex seen as an ISTJ?
About the reading people thing, I couldn't identify more with your insights, [MENTION=22067]riva[/MENTION]. I definitely read more into the MBTI than enneagram. Its way more interesting to me to understand the motivations of a person than the person through a more life historic perspective. Even though that's interesting as well.
Also, from a couples perspective this show gives us many of them. Going by my own definitions:
An ESTJ ENTP couple, no idea why they're together but they seem to compliment each other well.
An ISTJ ESFP couple, perfectly balancing each other out.
An ISTP ESFJ couple, that works out in a great way, even though they're different.
An ESTP ISFP couple, who work in a weird way.
This would make 3 couples that are Different in other than being an S and one couple that is a very weird combination but works well. Looks like the writers have made their homework on MBTI.