I've been using the free developer version of this over the past few months on Mac OS 10.3.9 to learn ColdFusion and its been quite enjoyable. I would like to give the developer's version a bunch of stars but I don't feel that I'm experienced enough yet to really be qualified to do so.

The only problem I had was that, being a novice to web app development and the ins-and-outs of servers, I could not get ColdFusion to run based solely on on Macromedia's installation directions -- they weren't complete enough for me.

For Mac OS X I’ve found the best installation instructions are at Community MX: "ColdFusion MX 7 on Macintosh OS X: Part 2." (Java 1.4.2 or better is needed):.
http://www.communitymx.com/content/article.cfm?cid=C5ACC

When I upgraded my version of MAMP (An free and easy to install application of MySQL, Apache, PHP, phpMyAdmin, etc.) ColdFusion could no longer connect to MySQL databases. I found that when using with MYSQL 4.1 or above the JDBC connector is needed and , in this case, Macromedia's instruction were sufficient to solve my problem:
http://www.macromedia.com/cfusion/knowledgebase/index.cfm?id=6ef0253

I hope this was helpful to any other beginners out there.