Red Hat Enterprise Linux 7 is going with the Linux 3.10 kernel by default. Of course, as with all RHEL releases, Red Hat will be doing back-ports and other kernel modifications to harden the kernel and make it enterprise-ready that's suitable for use for years to come.
Some other key components to point out from the Red Hat Enterprise Linux 7 Beta 1 is the GNOME Shell 3.8.4 desktop, X.Org Server 1.15 RC1, Mesa 9.2.2, PHP 5.4.16, and the GCC 4.8.2 compiler. The GNOME 3 Shell desktop is used by default in Red Hat Enterprise Linux 7 for those doing a desktop installation, but it's in the classic mode and not as much of a change compared to GNOME 2. In my past two days of usage, it worked out fine and didn't yield too much of a change. KDE4 is also available as an option for RHEL7.
For those that weren't RHEL6 desktop users, here's what Red Hat Enterprise Linux 6.5 looks like for reference:
Overall, my testing of Red Hat Enterprise Linux 7 over the past two days has been very smooth and pleasant.
For running some benchmarks on Red Hat Enterprise Linux 7, the Phoronix Test Suite was used. If running the latest stable release (4.8-Sokndal), the Phoronix Test Suite already runs great on Red Hat Enterprise Linux 7. Most of the test profiles hosted at OpenBenchmarking.org are also building great on Red Hat Enterprise Linux 7 but for some you may need to fetch some dependency packages from the EPEL6 repository for the more obscure benchmarks.