Linux 3.17 is a big improvement and brings a ton of great features like working AMD Radeon R9 290 support, Xbox One controller support, DMA-BUF cross-device synchronization, a lot of ARM hardware improvements, free-fall support for Toshiba laptops, Intel Braswell and Cherry Trail enablement work, EFI Xen Dom0 boot support, file-system improvements, and much more. Linux 3.17 is a very exciting update!
While Linus doesn't go into detail about all the new features like the aforelinked Phoronix articles, you can read his brief statement via the kernel mailing list. For some random bar trivia, Torvalds has kept the "Shuffling Zombie Juror" code-name for Linux 3.17, which has been the same since Linux 3.14 albeit changed in the Linux 3.16.x stable series.
Due to Linus travelling next week and the LinuxCon EU event the following week, Linus won't immediately start merging changes for the Linux 3.18 kernel but rather will be a few days out... Thus the merge window for Linux 3.18 will technically be open for about three weeks from now (roughly until 26 October). For Linux 3.18 we already have to look forward to many open-source graphics driver improvements, maybe OverlayFS, and a variety of other changes we'll be covering live over the 3.18 merge window followed by four Linux 3.18 benchmarks in the weeks ahead. We've already delivered a ton of Linux 3.17 benchmarks while more articles are still forthcoming.