BattleStar Shining / Lost Losing
I believe I'm mostly caught up on the two network shows I follow: BattleStar Galactica and Lost. The former is having a gangbusters third season, the latter losing its edge.
It's not an easy thing to make a good network serial drama. The form demands you have 25 episodes or so, each 45 minutes long and broken up by commercials. That's a lot of chapters to fill. Network executives mess with the work in progress trying to tease out better ratings, and they're usually not looking at making a great piece of culture, just how to get more eyeballs next sweeps.
The people who work for HBO have a much easier time of it: 12 one-hour episodes with no commercials and you pretty much get to make the whole thing. Input from the parent company comes in the off-season and you've got an entity that sees the long-game of DVD sales as a big part of their margin, so they want a quality product.
That being said, it's instructive to watch what happens as one show ripens and another deteriorates.