What modules does one need to get faster user experience? This probably leads to using ajax.

One of my thought is some node/%/edit's one one page. Preferably on tabs too!

Just browsing the categories http://drupal.org/project/Modules/category/101 (javascript utilities) and content at http://drupal.org is still overwhelming.

Here is a listing with just some modules.
- http://drupal.org/project/ajaxtable
- http://drupal.org/project/autosave
- http://drupal.org/project/block_refresh
- http://drupal.org/project/compact_forms
- http://drupal.org/project/cck_fieldgroup_tabs