For the FOI and CFI writtens I elected to use the electronic software from Gleim. I scored higher on those two writtens than I had on previous ones. I've always had trouble focusing on those books and given the nature of many regional interviews I would rather take approach #1 in HSLD's post. The software allows you to study specific sections or even questions, and unlimited practice exams.

I've heard good things about ASA's test prep software as well but have no experience with it.

I prefer the ASA guide. I like how it has a seperate book for figures etc. I used Gleim all the way through my CFII. My biggest dislike with the Gleim is that you have to flip back and forth between pages sometimes to look at figures and then flip back to look at the questions. I'll give Gleim this though, they do have pretty good written prep software. Again though it doesn't have a seperate book for the figures. All the figures are displayed on the computer which can get annoying sometimes too.

Just my two cents.