I downloaded and installed Apple's latest system update to my main workstation last night. Everything went smoothly, as now seems to be the case with all Apple upgrades, BSD be praised. Mac Net Journal has a good presentation of 10.1.5 features, plus interesting comments.
I've indeed noticed that Word and Excel, which I've updated a couple of days ago with Office X SR1, now take advantage of the Quartz engine to display text. Very cool.
Speaking of cool, I also checked my system's uptime before I rebooted after the update: 45 days. How's that for a laptop !