It's pretty much true. A client of mine run display and while the CTR is much lower than text, the CPC's are high enough that the RPM actually is the same or better than with just text ads. Different industries display can work for - but even in the best, the CTR is still typically horrible except for image ads which usually pay the worst.
Interestingly with my sites it varies. When summer comes and the travel display ads start showing, then everything's everything. But the rest of the year, meh. Thinking about scheduling it so that I just don't show images except for June through August.