Apparently, the list of known issues is shrinking, which indicates that the operating system is getting polished up. Apart from the expected upgrade of Safari 4 Developer Preview to the recently released Safari 4 beta, this new seed contains some other interesting updates as well.
Apple continues its Cocoa push, updating more and more parts of the operating system to use it. The Finder has been the focus of the Cocoa love fest in this build, such as the Desktop, Get Info window, and Contextual Menus. The QuickTime player has gotten a new minimal user interface, following in the footsteps of Windows 7's Windows Media Player, which also introduced a minimal user interface.
A lot of work is also going into something very mundane: text. Snow Leopard will have all sorts of small new features that should make working with text a little easier, system-wide. For starters, the automatic spell correction of the iPhone has made the transition to its big brother on the desktop, albeit without the pop-up bubbles. The user just needs to press the spacebar to fix obvious spelling mistakes. Applications that make use of Core Text will all support this feature.
That's not all for text, though. Apple also introduces substitutions, a feature coming from PalmOS and Microsoft Word. Simply put, it for instance means that if you type "(c)", it will be replaced by a proper copyright sign (joke alert: should make those cease and desist letters easier to write, ey, Cupertino?). Users can also define their own substitutions. It's a Core Text feature, so should be system wide.
Services for text have become easier to access, via the context menu for selected text. For instance, you can select a bit of text, bring up the context menu, and it will include an item that says "send to Mail". Transformations are new, and allow you to transform selected text to all caps, for instance, or vice versa. Handy if you accidentally typed something while caps lock was on.
Data Detectors, which come from NeXT, have also been made system wide. Right now, they're already in Mail, where they identify phone numbers, email addresses, etc. or offer to turn an email into an iCal event. In Snow Leopard, they will be system wide, which makes them even more useful than they already were.
The text features are exactly the type of thing that separate Mac OS X from Windows, Linux, and others when it comes to well-thought out, small, but extremely handy features that developers can implement simply by using the various Core frameworks in Mac OS X. Forget the RDF, forget the cultism: Mac OS X simply has a lot of these features that genuinely make the operating system easier to use than Windows and Linux in a number of areas.