The changes in the game over the 3 years, is almost equivalent as the differences between Sim City 4000, and Sim City Societies.
very simply, they dumbed it down A LOT.
Why? Dunno, they havn't said yet. Maybe if they gave the players an explanation as to why so much was taken out, maybe people wouldn't have gotten as annoyed. It could have easily been a technological problem, or would have required CPU power that only high-end users would own, thus shunning out 90% of the gaming market. Don't know. They haven't told us.
At the same time, the players never got any news from EA/Maxis saying that the features that really made us drool in the '05 tech demo, was taken out. ( at least, I'm not aware of them telling us anything of the sort. ). So it appears as if they took out a lot of the features, didn't say anything, and just let the players assume those features would still be in the game.
Again, I don't recall them every telling us about the changes. They may have...and i could be 100% wrong on this.
But it would be like if WarHammer online cut out PVP in the retail version, but not telling anyone, and letting the players find out for themselfs.