I was looking forward to this article, because I was curious how the designers view and approach party building. Before diving into the article, I'm going talk about my personal take on the subject.
In 3rd Edition I didnt much care for party composition outside of "someone needs to play a cleric". Depending on the players and raw numbers, we could occasionally get by with a favored soul or even a druid if we absolutely had to. This was because while prior editions utilized parties of adventurers, each character was largely self-contained and didnt interact much beyond the cleric spamming cure whatever wounds spells to keep the rest of the gang propped up.
4th Edition relies on teamwork far more than it ever did before. My group preference is that someone plays a leader, and everyone else can just do whatever. We really like having a defender around, but its not always necessary depending on the overall fire-power of the group: we just like being able to burn through healing surges with minor actions is all.
The article itself runs ten pages. You get a basic rundown on the party building approach, which can be divided into two methods: they either build the party in a vacuum or they dont. I personally prefer my group to actually communicate at this stage to avoid lumping up too many roles, but more importantly I find that they can stimulate eachother and come up with better characters than they might have in isolation.
Then there's a brief recap on the four roles, which expands the definitions we got in Player's Handbook by a lot. Its mostly stuff we already know, but for newer players it might prove useful to explain things in more detail.
There're a couple tables on multiclassing combinations and which races do best and crappy in which classes, which again is great for newer players.
My favorite section is Party Themes. This is a rundown of various role and power source combinations, which reminds me of that old Final Fantasy challenge where you were supposed to beat the game with four white mages.
One example is called Tanking, which is a party of one controller, leader, striker, and two defenders. I'd like to see how well a party does with one or two leaders, and the rest as strikers.
Power source themes are just parties where everyone has the same power source, which also has a lot of appeal to me from a challenge perspective (whether the author wanted it to be one or not).
Its an interesting, short read. I think most of it is great for new players, but even for me I got something out of it.