Over Ubuntu 14.04, the Ubuntu 14.10 "Utopic Unicorn" in its current development state has the Linux 3.15 kernel (but will end up using Linux 3.16), Unity 7.3.0, Mesa 10.2 (10.3 should make it in time for Ubuntu 14.10), and GCC 4.8.3 (while GCC 4.9 should make it for 14.10).
I ran some benchmarks on an ASUS Zenbook Intel Core i7 ultrabook to compare the performance of clean installs of Ubuntu 14.04 LTS against Ubuntu 14.10 (using the daily ISO as of 3 July). All of these initial benchmarks can be found via 1407047-KH-UBU72218440 on OpenBenchmarking.org. As you can expect though considering this is just a quick one page posting on Phoronix, the results aren't really dramatic or different for that matter. As Ubuntu 14.10 matures and further deviates from the state of the Trusty Tahr, we'll be back with more Ubuntu Linux performance benchmarks on Phoronix.