Articles about updates to Mac OS X updates are starting to become repetitive to write. The 10.X.1 update is a quick fix for the most egregious bugs, and was probably in progress before 10.X.0 was released (see “,” 16 August 2011). The 10.X.2 update actually makes some substantive changes in behavior and fixes additional serious bugs (see “ ,” 15 October 2011). And then we come to 10.X.3, which is where Apple starts knocking off obscure bugs that relatively few people have encountered — all subsequent 10.X.Y updates will continue in this pattern.
(As always seems to happen after Mac OS X updates, we’re seeing quite a number of reports of problems after installing 10.7.3. The solution, either preventative or after the fact, seems to be to use the combo updater. If any common problems start to bubble to the top, we’ll call those out. As of 6 February 2012, the most serious is the “CUI bug” and associated crashes, which seems to have caused Apple to pull the delta update in favor of the larger combo update; Software Update is providing only the combo update now. Lex Friedman at Macworld.)
Mac OS X 10.7.3 Client -- You know you’ve started down the 10.X.3 path when the first bullet item in the release notes for is “Adds Catalan, Croatian, Greek, Hebrew, Romanian, Slovak, Thai, and Ukrainian language support.” Don’t get me wrong, support for these languages is extremely welcome (and if you’re in one of the associated countries, undoubtedly long overdue), but it doesn’t change the behavior of Lion for most — or hardly any — existing users. Slightly more relevant to existing users is the usual addition of raw image compatibility for newly released cameras. There are no new features that I’m aware of yet.
All other changes appear to be bug fixes, addressing problems related to using smart cards to log in, compatibility issues with Microsoft Windows file sharing, a problem printing Microsoft Word documents that use markup, a graphics performance problem after sleep on some earlier iMacs with ATI graphics cards, a Wi-Fi connection problem after waking from sleep, an issue that could prevent Safari from opening before joining a wireless network, a number of fixes related to Active Directory, and a possible issue authenticating to an (I had to look it up too).
As always, there are oodles of in 10.7.3, relating to vulnerabilities in (deep breath): Address Book, Apache, ATS CFNetwork, CoreMedia, CoreText, CoreUI, curl, dovecot, filecmds, ImageIO, Internet Sharing, Libinfo, libresolv, libsecurity, OpenGL, PHP, QuickTime, Subversion, Time Machine, WebDAV Sharing, Webmail, and X11. Plus, Mac OS X will no longer trust SSL/TLS certificates issued by DigiCert Malaysia, which has issued certificates with weak keys that it cannot revoke.
For those who haven’t already pored through the list of security fixes, you can get a sense of what Apple has done by the names. There are fixes to well-known applications or technologies you recognize, like Address Book, QuickTime and Time Machine. Then there are fixes to popular open-source software that’s built into Mac OS X, like Apache, curl, PHP, and Subversion. And finally, there are fixes to code libraries or frameworks used by all sorts of Mac applications — these are the things you’re least likely to recognize, such as CoreMedia, ImageIO, libresolv, and libsecurity. Knowing what components have been updated isn’t helpful to most people, and while it can be distressing to see so many components needing help, it’s good that the vulnerabilities are being fixed.
The easiest (and fastest — it’s only 730 MB on my MacBook) way to get Mac OS X Lion 10.7.3 Update is via Software Update, but you can also download the (997 MB) and  (1.2 GB) updaters. (Right now, the delta update link is redirecting to the combo update page.)
Mac OS X 10.7.3 Server -- The 10.7.3 update would seem to be a much bigger deal for those using Lion Server, to judge from the release notes for.
To start, the Server app has received numerous interface improvements, which reveal added functionality. The File Sharing pane now displays the number of users connected via AFP and SMB and has a new Connected Users tab that displays details about those connections (user name and idle time for AFP, and client IP and connection type for both AFP and SMB). That tab also enables admins to send messages to AFP-connected users and to disconnect them, with or without a message. Lastly, admins can create a greeting that will be displayed to users who connect via AFP.
In other file sharing changes, Lion Server 10.7.3 fixes a number of issues for Windows users accessing files on a Lion Server SMB share, including problems with copying files with certain extended attributes, saving files in Windows 7, opening files with Microsoft Office 2003, and creating new folders in Windows Vista.
The VPN pane of the Server app now provides the option to enable the VPN over PPTP and to save a PPTP configuration profile for distribution to users. When PPTP is enabled, PPTP clients share the same address range as L2TP clients. Apple has about Lion Server’s PPTP support. Finally, admins can now set DNS server addresses and search domain names for VPN clients.
The Server app’s Web pane now enables admins to edit a site’s domain name after creation, choose a different SSL certificate for each site, map multiple domain names to a single site, configure redirects and aliases, specify custom index files, and use .htaccess files by selecting the Allow All Overrides checkbox. All good stuff for those running Web servers in Lion Server.
There are also notable improvements in iCal Service, Mail Service, Open Directory, Podcast Publisher, Profile Manager, Server Admin, Wiki Service, and Xsan. The have full details, plus links to some additional support articles.
Software Update will give you a custom version of Mac OS X Lion Server 10.7.3 Update, of course, but you can also download the (1 GB) and  (1.34 GB) updaters. (As with the desktop version of 10.7.3, the delta update link is currently redirecting to the combo update page.)
Finally, in conjunction with Lion Server 10.7.3, Apple has released, which provides  to Podcast Composer, Server Admin, Server Monitor, System Image Utility, Workgroup Manager, and Xgrid Admin.