It's a learning material. From all discussion about Linux tracing I get a feeling that no Linux kernel developer seen DTrace in action. And no one exactly knows what they compete against. It would be nice if kernel developers tried DTrace, learn about problems it helped to solve (there are many reports on blogs) and saw how powerful yet easy it is.
DTrace is wonderfully usable by Joe random admin and is generic enough to stop blooming of specialised tracing frameworks. Sure, latency top is cool, powertop is cool, usbmon is cool, blktrace is cool, but each of them needs its own hooks in kernel. On Solaris, powertop is implemented on top of DTrace, without modifing kernel.