I noticed that it also states that it uses worker threads to manage tasks, and I've only had a quick glance at their source code. There are some interesting aspects of QFuture from a quick read, namely the fact that you can cancel / pause / resume a task.
What I don't see is support for scalable memory allocation, although I haven't investigated in detail. I also don't see anything like tbb::pipeline which would be very useful in graphical interfaces.
It appears that Qt Concurrent is going to be incorporated into Qt version 4.4.
Take a look and let me know what you think. It would be an interesting project to make a Qt Concurrent-compatible interface which uses TBB on the backend. I've posted to the Qt Concurrent forum as well to mention TBB.
I'll write a blog about Qt Concurrent vs. TBB when I have some time to investigate and perform some benchmarks (in a week or so).