I have an iPad that I have to start using at work. We are currently working on updating some of our excel documents to the ipdad and I need to know if there is an app that will allow the use of dropdown boxes. A lot of our documents ask questions and the possible answers are in dropdown boxes.
You might want to have a look at Apple's Numbers app. They have a Help section on the Apple iWorks site devoted to it, so you should be able to determine if it will do everything you're looking for.
If you need the link, or some Member's reviews, let me know.
Numbers won't do drop down boxes. I don't know about the other solutions.