It turns out that the Epson PIM technology (based on Exif 2.1) is essentially a proprietary hack and it's largely been replaced by the Exif 2.2 standard which is also evangelized as Exif Print.
Our old Nikon Coolpix 995 produced Exif 2.1 jpegs while our new camera, a Nikon Coolpix 5400, produces Exif 2.2 jpegs. The Epson PIM plug-in distributed by Epson UK only works with Exif 2.1 while the Epson PIM plug-in distributed by Epson US works with Exif 2.2. Think I can use the US version? The US Plug-in doesn't support our UK printer (an Epson Photo Stylus 950). Arrrggghhh!!!
I've logged a support call with Epson to ask about this.
Photoshop 6.0 by itself ignores Exif information but from reading the newsgroups, it sounds like it's common practice to ignore Exif information in Photoshop 7.0 entirely and just assign images to the Adobe RGB colour space.
Maybe this whole issue is moot? It sure is confusing. Maybe if I upgrade to Photoshop CS, everything will just work? Yeah right!!