Not far ago we've completed the project regarding development of a custom timesheet for one of the companies for which we work for. It took a liitle bit longer then we first assumed but the outcome seems to be outstanding. "The company" had a problem with calculating costs on each project. They also wanted to make sure they will get the ability to apply changes constantly.
We decision was simple - virtualisation + development of the custom module which they've applied to Drupal 7.
Currently they have over 100 000 nodes and everything seems to work correctly.