Are water and CO2 all we have to worry about?

No. Other gases can absorb in the infrared and contribute to greenhouse warming, including methane, ozone, CFCs (chlorofluorocarbons) and nitrous oxide (released by nitrogen-based fertilizers). 

Of these, methane is the most important. Its concentration in the atmosphere has more than doubled since preindustrial times. Sources include the biological activity of bacteria in paddy fields and the guts of cattle, as well as the release of natural gas from commercial oil and gas fields and landfills. 

Molecule for molecule, other substances are even more potent greenhouse gases. A single molecule of either of the two most common CFCs has the same greenhouse warming effect as 10 000 molecules of CO2.

the greenhouse effect is a thoroughly bad thing?

Not quite. Without it, the planet wouldn't be warm enough to support life as we know it. The problem is that beneficial natural levels of greenhouse gases in the atmosphere are being boosted by human activities, especially the burning of fossil fuels. If nothing is done to curb emissions of CO2, for example, the amount of the gas in the atmosphere will have doubled by the end of the 21st century compared with preindustrial levels.