Some of those complaints are typical ones from people who do not like change. But others are serious bugs with the interface.
For example, to access the search tools, it should work like this:
But some are seeing the options not expand and format weirdly, like this:
There are several other complaints about the search tools option not working in the Google Web Search Help.
Albert from Google is collecting feedback from these users to see what browsers and operating systems they are using. I am suspecting this test might become a reality in the near future.
Note: I am able to replicate this in Chrome while incognito mode for some searches and had some issues with the search tools button working. But after refreshing a few times, it did indeed work. So this might be a caching issue on some browsers. Note, I really think this is being rolled out soon.
Forum discussion at Google Web Search Help.