This is no longer true. We now have second-generation NoSQL data stores that provide strong consistency, fault-tolerance and ACID transactions, based on the sharded NoSQL architecture that scales easily.
If you're exposed to the accretion of business requirements you do not control, you'll eventually be pushed toward a definition of "power" that relational databases meet the best... except when the dataset gets large.
What you say is still true, of course, and will only become more true over time. As more work is put into technologies, they tend to become more well-rounded. Languages that used to have awful performance (100x C) are now closer to 3-5x, for one example. The best NoSQLs now have many of the traditionally relational benefits, and the best relational databases (e.g. PostgreSQL) are overcoming traditional deficits associated with "relational".
http://www.cs.cornell.edu/johannes/
and
http://www.cs.cornell.edu/annual_report/99-00/Demers.htm
?
More seriously: Al, Johannes, and many other notable researchers in the DB space have complex, nuanced opinions on NoSQL systems. And these opinions are being revised daily as new information comes in; we've seen some researchers go from decrying the whole NoSQL movement to becoming some of its fiercest proponents, seemingly overnight. I would do them disservice if I were to try to present them here.
So I'd encourage you to ask them directly. Or perhaps we could have a panel at a conference. That'd be fun if done right.