With SSI does the whole page still refresh? If so it doesn't matter that much if the page is cached because there is still going to be that lag time where the navigation will dissappear for a second. Frames can be really efficient and beautiful. So can flash, CSS or whatever you chose to build your site. It's really execution, quality and content, not so much the method. This whole "frames are dead" is the same nonsense we go through every couple of years. You can add it to the list of:
1."HTML is dead" (from the Flash, xml and dhtml crowd)
2. "Print is dead" (without a hint of irony, many books, magazines and carrers were devoted to this in the mid/late 90's)
3. "Irony is dead" (too cool for anything crowd)
4. "Microsoft Windows is dead" ( linux and mac users)
5. "Google is dead" (every tech wannabe writer in the press who wants to sound edgy)
6. Disco is dead (yeah right, go ask Madona and Britney Spears about this one)
7. Grocery stores are dead (from Web Van investors)
8. "Search engines are dead, the portal is king" (1998-2000 from the portal crowd)
9. "Portals are dead, search is king" (2000 on, from the portals themselves)
The list goes on, and on and on.
How about "Absolutes are dead"
Different strokes for different folks.