Why is that that they have cleaning discs on the market for pc's but not for xbox, playstation or wii? When they develop these things, they could at least make a cleaning disc for the laser head that reads the discs. The ones for the pc's doesn't cut it
Canned air is good if the device is open as the dust needs to come out. The problem is if you open your console the warranty will be voided. Blowing air into the console when still sealed won't do any good as it will only just move the dust within it.
You just need to know how to do it correctly. For cleaning off the laser lens you need only apply one quick blast to the right spot. Doesn't really matter if the dust comes out as long as it is off the lens, which is the OP's goal.
If you want to completely clean out the inside of the unit, then yes opening it would be the best way... which of course you shouldn't do if it's under warranty or you ever want the option to send it in for repair.