Quite a few badly written apps like to create folders in specific locations, and expect them to be there and nowhere else. For example, my ~/Documents folder contains items such as 'Microsoft User Data', 'Steam Content', 'TomTom', etc. Some even create folders in your home directory or worse, at the root level of the hard disk!
Sometimes you can set a different location in the preferences of the application, but sometimes there's just no way. If you move the folder, the application will become hopelessly confused and/or create a new copy where it expects it. You can make these folders invisible, but then you can't easily access them anymore.
Apple released Java for Mac OS X 10.6 Update 3 (and a corresponding Java for Mac OS X 10.5 Update 8) through Software Update shortly after the Back to the Mac event. The general release notes are here and the security fixes are listed here.
However, those are not the most interesting items about this release.
After you performed a Time Machine System Restore, and you start to open some documents in Finder you will get prompts of the kind 'You are opening the application XYZ for the first time. Are you sure you want to open this application?' as if your computer was freshly installed, not having any file/type associations.
Why this is happening: the Launch Services Database was somehow not restored. Its settings were cached, and cache folders seem to be ignored in the restoration process (for good reasons).
If you want to easily and efficiently control/edit the file/type/mime/URL-scheme-handler associations, then I recommend the preference pane: RCDefaultApp
[crarko adds: I haven't tested this one. RCDefaultApp has certainly been a useful tool to have around for a number of years now, and is still good in Snow Leopard. (Removed an erroneous assumption of mine.]
One missing element of Time Machine has been the ability to encrypt the backups. There have been suggestions of ways this can be done to an AFP connected network share using a sparse disk image, but not on a directly connected device. The method below shows how to accomplish this on a local volume.
One of the occasional irritations of working with launchd is that it doesn't naturally expand shell wildcard characters (~,*,?,...). This means that full paths have to be spelled out for all files: an annoyance at best, and an obstacle when commands need to select specific groups of files or do work across different home folders. For example, a command to clean certain files from a user folder when any user logs in, which is simple enough to write in the shell -- rm -f ~/Folder/*.xxx -- fails when written into a launchd plist.
Occasionally the bluetooth process can decide it doesn't want to connect to any devices. Turning bluetooth off means you can't re-enable, but with Bluetooth Explorer, you can force it to do so.
When in this broken Bluetooth state, trying to connect to any Bluetooth device will cause an error. I usually try turning off Bluetooth when it has issues, but in this state it will refuse to turn back on (the menu bar option for 'Turn Bluetooth On' is greyed out). I'm sure a restart would fix, but I've found that if you have the Developer Utilities installed, Bluetooth Explorer.app will do the trick.
Simply start up the app, located in /Developer/Applications/Utilities/Bluetooth/, and it will give you a message about turning on the controller -- ignore this, as it doesn't seem to help. Once it's started, go to the 'Utilities' menu and select 'HCI Controller Selector'. In most machines, I think you'll just have one 'Apple Inc, Bluetooth USB Host Controller.' Select the controller, hit 'Activate', and Bluetooth goes back to normal.
[crarko adds: I don't know if this is just 10.5 specific. I've never encountered the issue. However, the Bluetooth Explorer utility can provide a wealth of information about not just your controller, but any Bluetooth device it can detect. Go to Devices» Show Device Discovery and then select a device and click 'Get Device Info...' It's a handy little app.]
Mac OS X users have not needed the ability to defragment their hard drives. Most defragging is done in the background by the OS. There is one caveat: OS X does not defragment files larger than 20 MB. Quite often, many game files are easily larger than 20 MB. Fragmentation of game files will negatively impact performance of games, particularly FPS games.
Valve has included a defragmenter in the Steam client. Each game installed can be selected and right clicked to bring up the properties box. Once in the Properties box, select the Local Files tab and click Defragment Cache Files to begin defragmenting the game.
The author's blog has some screenshots of the process.
[crarko adds: I haven't tested this one. Here and here are some good discussions on the 'Hot-File-Adaptive-Clustering' method Apple uses in HFS+, and its effectiveness. On the whole it's been quite good. The 20 MB file size limit mentioned is one of the limitations, along with the number of extents used. I don't know if you still need to be wary of defragging a FileVault home folder, but I'd err on the side of caution and make sure I had a known good backup before trying it.]
iStat is a great program for keeping track of your system by displaying menulings showing CPU usage, memory usage etc. In Mac OS X menulings (also called menu extras) are managed by a program called SystemUIServer.
iStat appears to have a memory leak where over time, the REAL memory used by SystemUIServer grows basically without bound. Memory usage that should be around 40MB balloons to 300MB then to 1.3GB over a few weeks of never rebooting. This would be bad enough if it was the virtual address space that was being used up this way, but this is real memory, causing real memory pressure and real swapping.
Obviously the ideal would be for Bjango to get on the case and fix this bug. Since they appear unwilling to do so, I have come up with a workaround.
The availability of software like Perian and Flip4Mac that make non-Apple video formats available to QuickTime and players like VLC and MPlayer means that many of us have files in formats like Flash and Windows Media Video that Mac OS X's Spotlight metadata subsystem recognizes as 'Movies' but for which it cannot determine video-specific metadata like dimensions, codecs, duration, and bitrate. It is possible to fix this in Leopard by duplicating and modifying a piece of the base OS, but in Snow Leopard it takes a bit more effort.
(This hint is also useful for 10.5 and probably 10.4, but 10.6 adds a special twist.)