The primary reason for switching to Pressflow is to use an HTTP accelerator such as Varnish
Apache Configuration
Adjust your Apache configuration to server the Drupal site on port 8080. Edit your Apache conf file and add:

Restart Apache and make sure you can access your site on that port.

Varnish Configuration

Add Pressflow base to your Drupal SVN repo
Assuming you have your Drupal repo checked out in /tmp/drupal, create a base folder for Pressflow:

Add/Upgrade the current version of Pressflow to your Drupal repo
Then download the current version of Pressflow and load it into the repo:

cd /tmp
wget http://launchpad.net/pressflow/6.x/6.20.97/+download/pressflow-6.20.97.tar.gz
tar zxf pressflow-6.20.97.tar.gz
rm -f pressflow-6.20.97.tar.gz



$contentType = 'node_type';
$nodeList = db_query("SELECT node.nid AS nid FROM node node WHERE node.type in ('$contentType')");
while ($node = db_fetch_object($nodeList) ) {
$nodeId =$node->nid;

$nodeRevList = db_query("SELECT `nid`, `body`, `teaser` FROM `node_revisions` WHERE `nid`=$nodeId");
while ($nodeRev = db_fetch_object($nodeRevList)) {
//echo $nodeRev->teaser . "";
$teaser = node_teaser($nodeRev->body,NULL, 200);
//echo $teaser;
db_query("UPDATE node_revisions SET teaser = '%s' WHERE nid = %d", $teaser, $node->nid);
$i++;