Not sure why we are talking about OS X here. Let's stick to Windows. 
[ul][li]a) Folder sizes are never refreshed automatically, only on-demand. Auto-refreshing folders would probably be a performance drain.
If file sizes or other metadata are not being updated, see Changes to folders are not always detected for debugging steps, and please post the debug output so we can see if it indicates anything unusual (e.g. the device could be reporting the change notifications using different paths to what Opus is expecting, if there is more than one way to represent the paths on that device).
It's also possible the device is not generating change notifications at all, or is only sending some, or has a long delay before it sends them. If so, the problem may lie with the device, drivers or filesystem involved. The debug log can help reveal that as well, if it is what is happening.
If something in the system is generating a huge flood of change events, it can also cause events to start being dropped. As with the other possibilities, the debug logs will show it as well.
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[li]b) Was there a b?
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[li]c) Drag & drop from archives to other programs works, provided the drop target supports streams, which not all do. If it didn't work, you wouldn't be able to drag files from an archive to the Windows desktop.
Double-click and the Open With menu and various commands (e.g. to run a program with the filepath given) can all be used to extract files to temp and then pass it to the program, too. Just not drag & drop, for numerous technical reasons.
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[li]d) That sounds like something which was fixed recently. I'm not sure if the fix has been released yet but I remember Jon working on something like that.[/li][/ul]
(General point: This thread is in danger of becoming spaghetti if we talk about all of these things at once. One question per thread is best.)