I recommend the evenhanded article by Michael Hirsh, "Was Keynes Right? We're about to plunk down nearly $1 trillion on a bet that he was. But no one's sure." It reflects the uncertainty among even the experts about this massive stimulus plan. I tend to agree with his assessment that we have to try the experiment, but we had better be clear that is it an experiment and it may well not work.
Personally, I think the odds would be better if we would just bite the bullet and do the painful things we need to do to the banks. Japan tried this stimulus approach in the early 1990's, and it didn't do much for almost a decade until they finally dealt with the banks instead of propping them up.