Since the update is the same release as the DVDs (r6) I would say NO it would not be useful.
Someone that installe Debian 4.0r5 or earlier and hasn't been keeping up to date over the internet..
I wouldn't bother downloading any of that unless the machine I needed it for didn't have a broadband internet connection.
the Debian Netinstall method is faster to install (if you count all download times involved) and I probably download less than 1 GB worth of data for a single install vs the 13.4 GB of data those 4 DVD iso images would be.. Doing a netinstall also give you the advantage of getting that latest updates DURING the install so when the install is complete the system is fully up to date.. Something to keep in mind.
Hope that answers your question