I recently bought a Holga 120s for my girlfriend, and she's running her 1st film through it now (35mm), so we're yet to see if it's any good. Before she even started I made sure the film counter window was taped over.A good site for Holga tips is here :Holga Tips
I've never used a Diana, but I understand that Hogla's and Diana's share many of the same quirks.