When we build our Agile PM application Acunote one of the main requirements was than entering and updating tasks should be as quick, and require no more actions than in Excel.  To that end everything is shown as a list, and you can edit task description, status, owner, estimate and remaining with 1 click.  AJAX web application can/does offer advantages over Excel, but when building it it's important not to lose track of the strength you liked about Excel approach in the first place.