SPYW certainly seems like the only real, new issue. It seems to me like a clear case of sacrificing a product's short-term quality for long-term quality. I.e. diverting as much traffic as possible to G+ will drive up usage, which will give Google more data on which to optimize search results.
It strikes me as analogous to Apple's move from OS9 to OSX. OSX performed poorly at first, but it was a necessary if painful infrastructure change for the sake of the product's future.
Another reason I'm not worried is that Google's only lock-in is search quality. If a challenger appears and really does perform better for searches, then people will eventually shift over. I think this is ultimately what will keep Google from going completely off the rails vis-a-vis search.
Conversely, I think it's what allows Facebook to get away with a lot. Its lock-in feature is ubiquity/network-effect, which is at best orthogonal to quality of product.