Multi-Column joins have been enhanced to not require materialization of concat_attributes already a while ago.
In SPS 9/10 it's even possible to have them persisted selectively per model.
Generally speaking, at least in my experience, the largest performance gains/losses don't happen on this level of implementation, but before.
Understanding of the data, the data model, and the requirements usually make or break performance.
The concat_attributes were most often discussed due to their "silent" creation and hunger for memory - not so much due to their performance impact (- actually they are there to improve performance)
- Lars