Views 2 has an option to have exposed filters update the view using AJAX. but the AJAX update is triggered only once the "Apply" button is pressed. If you want the AJAX update to happen automatically as soon the filters are changed you can add your own behavior in your own module to hide the apply button and trigger its submit on change of all filter fields as shown below.
Drupal.behaviors.modulename = function (context) {
$("form#views-exposed-form-viewname-page-1 #edit-submit").hide();
$("form#views-exposed-form-viewname-page-1 .form-text").change(function() {
// Execute the submit function on the form
$("form#views-exposed-form-viewname-page-1").submit();
});
