Here we go again. The perrenial WD40 debate. I predict 7 pages for this thread.

WD40 is a mild lubricant and a mild solvent, about the same solvent/lubrication qualities as kerosene or deisel fuel. It will not damage your chain, it is more then adequate to lube it, but its a pain to use, since it sprays all over the place, getting all over the wheels anf frame. not just the chain.

About the only thing I use it for is to flush out my 105 shifters occassionally. First I hit the shifting mechanism really hard with a strong stream of water from a hose, then use about a quarter of a can of WD40 as I shift through the gears.