I've found that the next button conditional logic will not work without the form conditional logic turned on. I'm just assuming this is a bug. Without the next button logic on, form conditional logic off, Firebug reported "gf_apply_rules is not defined". So I did a test, and it turns out that when you're only using the next button logic, the "conditional_logic.js" is not included in the HEAD as it should be. Turning on form conditional logic fixes this with ease, but shouldn't be necessary, right? I mean, you should be able to have page logic sans form logic.