I too agree that the interface leaves much to be desired. Frame was originally developed on UNIX (ported to all flavors: AIX, HP-UX, Solaris, etc.) and it still supported on just about every UNIX platform along with Windows and Mac. Adobe noticed that Frame held a unique corner of the market that they knew no other DTP product offered: long doc support and the ability to handle global updates with absolute ease.
I've asked a person from Adobe's technical marketing dept directly why the interface hadn't been touched since Adobe acquired it 5 years ago, and he said 1) "current customers are comfortable with the UI" 2) "it would be a big undertaking". In short, the code is ancient and to go through a rewrite all that code would apparently take an extreme amount of time and resources. While this may be true, I think this quote from Tom Arah at Designer-info.com sums up the problem nicely:
"FrameMaker's underlying principles and layout engine remain as powerful as theyve always been and for institutional users looking for long technical document handling and multichannel output it remains the most flexible choice. The fact is though, that with the paradigm shift to XML-based publishing and repurposing, FrameMaker should be stronger than ever and winning new markets rather than trading on its past. Unless Adobe stops bundling and gets coding that's simply not going to happen and FrameMaker will remain a niche option - mainframe rather than mainstream."
You can read his full review of Frame 7 here:
http://www.designer-info.com/DTP/framemaker.htm
Does Adobe want Frame to remain a niche tool? Who knows, but with a 2-year development cycle that yields very little with each release, it's hard to know what their true intentions may be. With the surge of technical communicators over the last few years who rely very heavily on Frame (I believe Frame is as important to tech writers as Photoshop to graphic artists) Frame should be even more powerful than ever. As a technical writer, Frame still remains the only tool I truly rely on for producing manuals and other technical documentation. I couldn't imagine working in a Word shop, especially with the thousands of pages of doc I have to manage now.
Adobe recently moved Frame development to Adobe India, which I believe could mean one of two things: 1) move Frame out of our US offices so we can focus on the products that "really matter" (Photoshop, InDesign, Illustrator, Acrobat, etc..), or 2) get Frame to a development environment that will take a fresh approach to Frame's development, while also allowing them to reduce the costs (being in a third-party country) it will take to overhaul the product. I can only hope for the second assumption.
We can expect the next release of Frame in another year, so only time will tell what Adobe's got in mind for the world's best DTP tool.