Android application developers often opt for a simple freemium/premium model, which, when we think about it, is great for everybody.
Let’s consider the Slideshow for Facebook app as an example. Instead of relying on other people’s comments to decide whether it’s worth paying $0.99 for your app, it makes sense to download the free version (in this case, feature-restricted, but other applications developers choose to put ads), use it for a while, and then decide for yourself if the premium version is worth your buck.
I personally see it as a more sustainable model than the vast majority of iphone apps for which you pay between $1-$4 just to realize later that it was totally useless…
Slideshow for Facebook APP is very good, I love it!