What TimeGraph can provide for end-users is performance improvements, for the open-source stack. See these overview slides (this related paper is also interesting) that go into detail about TimeGraph and do provide some benchmark results. Interestingly, this university project does happen to use the Phoronix Test Suite for carrying out its graphics performance tests (it's mentioned in the slides). How much faster can TimeGraph make things? The slide mentions, "It's getting competitive to the proprietary driver!" The GPU command scheduler is particularly useful if multi-tasking with workloads that target the GPU.
This work can also be beneficial in the area of GPGPU computing. In fact, you may be wondering why this open-source work is being done and why this TimeGraph discussion is taking place during the Nouveau discussion at XDC2011. The TimeGraph developers have collaborated with PathScale. Besides their new open-source compiler, PathScale is incredibly interested in GPGPU computing and doing so using an open-source stack.
PathScale is the company that previously offered free Fermi graphics cards to open-source developers, was wanting to port Nouveau to OpenSolaris, and recently has been working on their own fork of the Nouveau driver known as PSCNV. With the PSCNV driver they're primary interests are in maximizing the performance and bringing up GPGPU support. In fact, there is GPGPU support with this work. Stay tuned though for another article at an appropriate time.
TimeGraph sounds like quite an interesting project and I wish it the best of luck. I look forward to hearing more about it during the X.Org Developers' Conference. For those not in Chicago, I will be providing audio/video recordings on Phoronix and will be writing about some of the most interesting discussions as well. I'll also be live tweeting.