Initial results of Ubuntu 12.04 "Precise Pangolin" are positive for boot performance and lowering the power consumption, so here's some performance results to show how this forthcoming LTS release is running for different workloads:
The open-source Nouveau driver stack in Ubuntu 12.04 LTS (Mesa 8.0 + Linux 3.2 + X.Org Server 1.11.3) is currently borked for Nexuiz. The other open-source drivers work fine on Ubuntu 12.04 for running Nexuiz.
OpenArena at least runs on the Nouveau stack. Thanks to many upstream Nouveau improvements (Canonical can't be thanked for contributing any significant upstream patches to the project), the Nouveau Gallium3D driver in Ubuntu 12.04 LTS is faster. However, this driver snapshot does not have re-clocking support and its performance is generally much slower than the NVIDIA proprietary driver (along with being less power efficient due to a poor power management infrastructure).
EXT4 on Ubuntu 12.04 LTS appears to have a small drop in performance compared to the file-system with earlier Linux kernels / Ubuntu releases.
Running the Apache web-server is at a high-point for Ubuntu Linux in the past two years from this Intel Core i7 system.