Good UI design is invisible - if your UX designer is doing their job, you will never even think about them. For things like Search, GMail, and Maps, the user need's definitely come first, and then the elegant engineering is a byproduct as people try to figure how the hell to implement the product they have in mind.
The notable flops have been the ones that have been driven by an elegant engineering concept; in particular, one of the major differences between Wave and GMail is that Wave seemed to ask "What can we do, and how should we expose that to the user?" while GMail (pre-Labs) largely asked "What should we do, and how can we figure out how to implement that?"
> if your UX designer is doing their job, you will never even think about them.
UX is not something you can stitch on afterwards. Good UX is deeply ingrained in engineering and an omnipresent, pervasive focus of the team. I think that's what parent is referring to in regards to what Google is lacking.
That depends on the product. A 50/50 UX back end split is fairly common. But, some products need a simple interface and a ridiculously complex back end. EX: Weather map's.
The notable flops have been the ones that have been driven by an elegant engineering concept; in particular, one of the major differences between Wave and GMail is that Wave seemed to ask "What can we do, and how should we expose that to the user?" while GMail (pre-Labs) largely asked "What should we do, and how can we figure out how to implement that?"