Shellman said:
Are ready made adventures like The Shackled City worth buying and running as a DM?
The answer is a qualified yes.
I ran the Shackled City from the magazines, which took 11 months from start to finish, with roughly one session a week. In that time, the amount of preparation time I had to dedicate to running the game was cut from about 3 hours a week to about 1 hour a week. So, that's a saving of about 88 hours of my (very limited) time. That being the case, the investment of $60 (the cost of the hardcover IIRC) is a no-brainer.
And that doesn't even take into account the facts that the game was
better prepared, and ran more smoothly than a lot of my campaigns,
and that we ended the campaign with me jazzed about the prospect of running another game. (Just in time to move house, and find myself in a gaming group with plenty of DMs

)
I can't recommend the Shackled City highly enough.
As regards the question of published adventures in general, rather than campaign books like the Shackled City in particular, I would again say they're generally worthwhile. If nothing else, a published adventure is likely to give you a cool villain and a couple of set-piece encounters you can steal. With the heavily math-oriented approach of 3e, that's extremely valuable. Additionally, a published adventure can sometimes make the difference between a harried DM having something to run for a few weeks, and having to call off the game. That being the case, a subscription to Dungeon is something that every DM should probably consider.
However, it is worth noting that published adventures (and particularly the campaign books) are only worthwhile if you're actually going to get some use out of them. I can't justify spending $100 (or equivalent) on World's Largest Dungeon if I'm not going to use it, or buying the Drow War series for it to sit on a shelf. For a small module, that's no big deal. For an issue of Dungeon, it's also not really a problem - there will almost certainly be something I can use, and even if there's not it's only a few dollars.