The benefits of using ColdFusion is that it's really easy to learn and is very powerful. I have a number of coldfusion tutorials available on my web-site (with more being written) that range from
beginner to
advanced. You will quickly see how easy it is to learn.
While the main engine from Adobe is not open source (cheapest license $1,200) one of the biggest competitors
Railo has recently been accepted into JBOSS and will be going full open source (free) this year. Railo currently has a couple of pricing categories that range from $0 (community edition) to about $2k (for an enterprise license).