As of mid-June Google will be incorporating the loading time of your landing page into your quality score.
They have announced that current loading time evaluations are available on the keyword analysis page to review so well worth reviewing all of your landing pages now to make sure that they don’t negatively affect your quality score when this kicks in in June.
More details from Google are available here:
http://adwords.google.com/support/bin/answer.py?answer=87144&topic=14467
