For that reason, I only buy Humble Bundles which have games that I know 100% I would play to completion. (such games that have been in Humble Bundles include Bastion, Psychonauts, Darksiders and Dungeon Defenders). And I still have a massive backlog from the other excellent games in the Bundles.
At the moment, I'll pass on HB8, atleast until I see what bonus games are inevitably added to the Bundle.