The article (albeit the first in a series) doesn't seem to have any real evidence to support free or non-free being better. The two arguments put forth are:

1) Free apps are a "marketing expense" for future projects (to have a good project which will attract some clients)." 2) A "free app means having an opportunity to demonstrate your quality and later convert those users into paying customers for the full app"

I don't know how people will feel about the first. Personally I'm creating my own apps to get _away_ from my clients, not get more. :P

The second argument seems pretty typical and could be valid. Has anyone done some genuine research into this? I'd love to see some statistics comparing revenue from a large sample of:

1) Free, but ad supported apps 2) Apps with a free 'lite' version 3) Free apps with in-app feature upgrades 4) Non-free apps