If you're going to compare cap-and-trade to a tax, honest advocates need to compare apples to apples. We need to hear what a real-life carbon tax bill would be like. And we should have a few dozen tax experts in the room to laugh at us while all this is going on. The fact is, cap-and-trade isn't as complicated as it seems, and a tax isn't as simple as it seems. In the end, though, despite the admitted complexities of cap-and-trade, at least it wouldn't be embedded within an existing 100,000-page corporate tax code. A tax would be. I'd keep that firmly in mind whenever you hear about how simple and clean a carbon tax would be.
On a related note, Felix Salmon posts on what parts of cap and trade are economically feasible.