One annoyance of Photoshop/Bridge CS4 is that it won't read any existing custom File Info panels. These let File Info display XMP metadata from other applications such as iView or Expression Media, and they were written in a text file format which was reasonably easy to create and edit. In CS4 though, the panels are Flash-based and at first glance it looks like you would need to buy Flex Builder for the job. Uh-oh, not another solution for developers who need paying, rather than users who know what they need and might hack their way there?
I don't really have the energy or interest to learn Flex, certainly not ahead of current efforts to learn ActionScript 3 for my Flash site, Lua for some Lightroom ideas, or ahead of getting my beauty sleep (I don't need too much of that). But look at Gunar Penikis's last paragraph here:
Hey guys relax. CS4 does not support reading CS3 panels - the reason for this is that the old format is pretty crufty and the energy would be better spent on building a really flexible UI. So we chose Flex (Flash) to base the panels on. The SDK is available at: http://www.adobe.com/devnet/xmp/
Note that you don't have to buy Flex Builder but it does make life easier.
Most importantly there is a sample in the SDK call “Generic Panel”. This is a panel designed specifically to read an external XML file of properties and display them - similar to the way the old File Info worked. Since it is XML based you can use your favourite freeware XML editor to build your panel with. The XML format is pretty simple, especially if you are used to the old panel layout language.
Adobe have been very smart with this Generic Panel. It's a compiled SWF file, so you don't need Flash or Flex, and you just have to know your way around XMP namespaces and be happy editing XML. It's not a lot more than copying namespaces and field names from File Info's Advanced panel, and pasting them into the properties.xml file using an XML editor such as something like MS XML Notepad:
In the above example I'm calling Expression Media's namespace, and then defining a File Info text box which displays the Catalog Sets metadata. If you're familiar with this type of thing, it's pretty easy stuff, and you'll just need the File Info SDK at the bottom of this page.
I've put online my CS4 File Info panel for Expression Media metadata (donationware). And here it is, showing a panel which combines metadata which one would typically add in Lightroom, such as the keywords, and Expression Media metadata such as the Catalog Sets or custom fields.
On PC, put the panel in C:Document and SettingsusernameApplication DataAdobeXMPCustom File Info Panels2.0panels.
On Mac, put the panel into the Mac's Library/ApplicationData/Adobe/XMP/Custom File Info Panels/2.0/panels/, not in the user's Library area /Users/username/ApplicationData…. There's a bug somewhere - in the panel, in Bridge, or in the documentation.
One last thought is that Flash/Flex does enable much fancier and more powerful panels. I can imagine it's possible, for example, to access the Google Maps API and display a map inside the Bridge or Photoshop File Info panel (update: yes we can). Whether anyone will take advantage of this change, only time will tell.