I personally have no problem with cluster bombs as a weapon of war as a general rule.  Having said that, you cannot use them in an urban environment and claim that you are trying to minimize casualties and be precise in your attacks.  Cluster bombs are, by their nature, non-precise weapons meant to wipe out many people over a spread out area.  If there are civilians anywhere near them, they are going to be killed or maimed.

 The big problem with cluster bombs beyond their imprecise nature, is that they leave unexploded bomblets which can be set off by civilians long after the bombs drop.  So provided that you're not using them in civilian areas and you make some effort, after hostilities have concluded to clean up the mess, I don't see these as an innately unethical weapon.