The only difference...
..is that those chips are downgraded to existing production part lines. i.e. a P4 that gets downgraded to a Celeron or a Conroe that gets knocked down from an E6700 2.6Ghz to say an entry level E2140 1.6Ghz. AMD is creating an entirely new line of unplanned chips based on duds.
This is a huge set back in terms of marketing and PR. Everyone who pays attention to the CPU market (read OEMs, since Dell and the like are the real customers here) knows this move is 100% because AMD is having terrible fab problems with 65nm, and you're going to have to convince those people (again OEMs) that these tri's can be sold to Joe Sixpack. Can they take garbage and polish it shiny enough to fool the laymen? Only time will tell, but I'm not going to be holding my breath.
They could downgrade the "tricores" to dualies and probably make just as much money, even though they'd sell at lower prices, simply because you don't have to spend the money to basically create a new niche market in such a short time frame.
They're not going to make good margins on these chips, heck I'd be sursprised if they break even after all the advertising and sales pitches that are going to have to be made just to get OEMs to buy in and then convince Joe sixpack to buy one, and if Intel jumps into the marketing fray with ads bashing these gimped quads, then they're really going to be loosing money. If I was Intel's marketing department, I'd be pretty damn excited about rubbing AMD's face deeper in the mud over th next 4-6 months.