I have been running the 10.7.3 update and the 10.7.3 server update many times on 10.7.2 Macs in my classroom over the past few weeks, and I can possibly eliminate some theories:
In every case, the machines were 2008 and 2009 iMacs that were imaged from the same image on a server, so there was NO additional third-party software or extensions on the systems. They didnt have ANY third party peripherals plugged in.
About 50% of the time the updates finish promptly (about 15 minutes) and the rest of the time they take hours, or never finish. And it is different machines each time so theres on consistency as to the model or the particular machine. Still no solution.
I've been using the 10.7.3 combo update downloaded from Apple, btw.
Also, my MacMini 2,6 GB with OSX 10.6.8, has almost died after Apparently the trouble is not a problem of Macbokks, only. I started installing OSX 10.7 from a flash drive. It stopped after the installer asked me to restatrt the computer. Whatever I tried since than to get the machine running again failed. Unfortunately, I have no recent backup. The reason for changing to Lion was to save my "mac" email adress. Apple delivered the stick with no word or explanation, and there was no warning with the start of installing. I think, it's a shame for Apple, and no longer I shall recommand Macs. It is the first time since OS 6.5 that updating/upgrading makes such a serious trouble. It's true: Never change a running sytem. However, I still hope to find a solution as I need the contents of my hard disk.
Such a shame that you blame Apple for you not having a backup... but lets help you get you data.