Actually, right now is not a good time to launch an attack. Afghanistan is on the verge of overthrowing the Taliban government, once this takes place the Afghani's will support the new government and encourage the US to come and get Osama Been Porkin and will probably help us do it.
Until this is accomplished invading Afghanistan, will only solidify support for the Taliban.
When the Taliban fall, OBL's goose is cooked and I'm sure he knows this. You can bet our SF/Delta/Rangers are in places to intercept his attempt to leave the country.
OBL is right now exactly where GWB wants him, in the cross hairs.
Osama and the Taliban are dead men, they just don't know it yet.