I've been wading through McMillan's Options as a Strategic Investment, and on page 773 (in the chapter Strategy Considerations - Using the "Greeks") he said something interesting:
"Refer back to the table of strategies at the beginning of this section. Notice that ratio writing or straddle selling (they are equivalent strategies) have the characteristics that have been described in detail: delta is 0, and several other factors are negative. It has been shown how those negative factors translate into potential profits or losses. Observing other lines in the same table, note that covered call writing and naked put selling (they are also equivalent, don't forget) have a description very similar to straddle selling: delta is positive, and the other factores are negative. This is a worse situation than selling naked straddles, for it entails all the same risks, but in addition will suffer losses on immediate downward moves by the underlying stock. The point to be made here is that if one felt that straddle selling is not a particularly attractive strategy after he had observed the above examples, he then should feel even less inclined to do covered writing, for it has all the same risk factors and isn't even delta neutral."