I've been using ColdFusion 9 along with the ColdFusion on Wheels Framework for about 6 months now. I still consider myself a beginner, but I am comfortable doing most things I need to.
I recently started writing full CF Script components, and I'm loving the cleanliness of the syntax. I am disappointed to lose some of the simplicity afforded by CFQuery, CFLoop, and so on... but I can live without this for now.
Recently, a few people have mentioned that Railo has better CFScript support. I'm considering switching for that reason.
What things should I keep in mind, and how do the two platforms stack against one another in terms of functionality and ease of use?
Here are the things you need to look for as far as differences between Railo and ColdFusion. This page lists all of the things that Adobe CF has that Railo doesn't, and vice versa:
http://www.getrailo.org/index.cfm/documentation/compatibility/cfml-compatibility/