Except for the tty disabling (which is more inclined towards better security), decreasing swappiness, using preload, disabling unneeded services are directly related to increase in performance.
1. Preload: Caches applications priorly. Minimum requirements are 1GB RAM.
2. Disabling unneeded services dont need any clarification IMO
3. Decreasing Swappiness: This has been tested and found to be effective. Due to that reason, new kernels would support dynamic control of swappiness. For lesser RAM usage, swappiness would decrease to much lower values than the current fixed value: http://kerneltrap.org/node/1044
4. OO performance: http://www.blog.solarwind.metafy.org...fice-in-linux/