Yes they have come a long way in terms of performance. They have managed to get Drupal up to a medium scale. Considering this is the sweet spot where most websites top out, Drupal is a great solution.

The work I am more interested is is not how Drupal can perform as much as how it can scale. At present Drupal is very much limited by how it uses the database. It is very difficult to get Drupal to scale much beyond a few boxes.

While Drupal has its place, I also think there is a lot of room for growth. To be truly successful I think Drupal needs to become much more usable and be able to scale horizontally. That is not trivial in the present architecture, but I am glad that some people are taking this on.

-Marty

I too have been impressed with Drupal and its progress. For a case study of scaling a Drupal deployment you need look no further than the Drupal.org website itself:

http://drupal.org/files/issues/druapl-org-scaling-infrastructure-barcelona.pdf

From a user’s perspective I have definitely noticed better response and availability since these measures have been implemented.