Although Drupal 7+ runs smoothly on PHP 5.3, Drupal 6 still feels much better with PHP 5.2. Therefore developing for both D7 and D6 at the same time becomes much less painful when running both versions of PHP in parallel. How this can be achieved on Ubuntu 12.04?
Several days ago I have done few very basic performance tests to see how node.js server behaves compared to Apache when serving very simple pages.
All tests were executed on dual-core Intel T4200 2 GHZ machine with 4 GB RAM running Ubuntu 10.04 Lucid (with X).