Well, I checked out the blurb on Roma Imperious at the web site. One thing keeps me from being interested in buying it as a pdf or print prodict: it's not d20. Odd, as the original question is posted to this site.
What gets me interested in a product are the free downloads (teasers or previews or enhancements). It doesn't matter if it's a product in pdf or print or both. (I generally prefer print products, however.) For example, I would not have purchased Skull & Bones had it not been for the great, free adventure and maps on the Green Ronin web site. I ran that adventure without the book and used the maps, but I wanted more information. So, I went to my FLGS and asked them to order it. I think they got two copies. I bought one, and the other is off the shelves as well [sold]. Although I use less than 1/4 of the contents, I am very staisfied with it. I am a little disappointed to see the co-authors philosophy here (...BUY ANYWAY), but he's entitled to his opinion.
Coincidentally, this thread and replies promtped me to check out Fvlminata d20. That looks like it has potential. I would prefer it in print than as a pdf, but I might get in as a pdf to check it out for cheaper since it may not be exactly my cup of tea. There's just something better about having a written document.