Just a quick tip here. If you want to find out what changed in ColdFusion 9 at a tag/function level, there are three places you need to check. All of these may be found within the CFML Reference.
The first place is the listing of new tags and new functions. This one is kind of obvious.
The second place is the Tag changes since ColdFusion 5 and Function changes since ColdFusion 5 pages. This provides a list of all changes since ColdFusion 5. In my opinion, that's a bit much. Adobe should probably limit this to the previous past two versions. But in general, this is another place where you can find out about updates.
Finally - there is a third place. Unfortunately, the "Tag/Function changes..." pages do not have a complete history/listing of all changes. A good example of this is the cfgridcolumn tag. Notice how it has a History section? Notice how ColdFusion 9 added a bunch of new types? This was news to me until earlier today when Sam Farmer twittered about the date format. What this means is - it may make sense to run through all of the tags and functions and check the history section for things you may have missed.
Unfortunately, even this isn't quite enough. The cfdump page does document the new abort attribute, but it isn't listed in the History nor in the "Tag changes..." page.
Edit: Note - sometimes in the History field, the ColdFusion 9 stuff is at the bottom, not the top of the history!