It appears, that Google's result now depend on what language the interface has. That is, if you search with a german interface, but select "Das Web" (the whole web) you will still get mostly german results for most queries, while someone with an english interface will get mostly english results. For queries with many result there will be only a small difference between a general webwide search, a language specific search and a country specific search.
I guess, that Google noticed that most people actually prefer content in their language. But for people, who are fluent in more than one language, this significantly limits the options Google offers. I don't know how I can do language neutral queries now! When I prefer more global results, switching the interface language is tedious (especially for toolbar users) and the results are not clear.
I think they should have changed the default selection of the radio button instead of changing the ranking (and then ask the user if he wants to stay global when he changes to global).
I'm sure the CTR on same-language results was higher and that led to the conclusion that users would be more happy on average. The "average" is important, but as even Bill Gates famously noted, Google's quality perception is driven by the performance in the rarer use cases. There is too much uncontrollable/non-understood magic going on now, and this lessens the value of google as a generic tool.
Are english searchers aware that their "world wide" results are now biased towards english content? Previously, international appeared more often, and thanks to the "Translate" link offered a global perception of an issue! Now, this seems to be lost to a great degree, without the users being aware of it (Or maybe english queries are still language neutral? I don't know how to tell)
(Disclaimer: I work for search.ch, a competitor to Google in the swiss market. On the other hand I often do use Google, especially for international queries (search.ch only searches Switzerland), and I, as a user, see this limited by this change)