One of the things I do on a weekly basis is follow the kernel development that Red Hat undertakes for their future RHEL5 kernels. This is very interesting because you can check the changelog for fixes, new hardware support, backported features (eg. kvm) and newly supported stuff (eg. fuse, xfs) that is coming in RHEL 5.4.
We discovered xfs was coming to RHEL, new ath5k fixes prove helpful on a friend's laptop, and I was waiting for I/O accounting, kvm and fuse to hit these releases too.