I created an account with MultiPLX just to test this feature, so I can report first hand that it doesn't work right. A search as simple as querying for both Amazon and Apple didn't return the results I expected. Ideally the search results should only include posts that contain both words, but unfortunately the results included every post which contained either word.
One could argue that the results were valid, but it didn't help me find what I was looking for: posts that mentioned both companies.
But as disappointing as this news might be, it's taught me a lesson. I think I'm beginning to understand why so few news readers offer article search; it's clearly not the easiest feature to implement. Feedly is charging for it, and not even my preferred news reader BazQux gets it right.
BazQux, as much as I like it, doesn't always return all the relevant results There have been times that I know there were more posts than what was shown as a search result. For example, posts that mention both Amazon and Apple are quite common, but BazQux can't find them all.
But don't think I am unfairly beating up on the little guys; this is one feature that not even Google Reader got right all the time.
I know we all like to hold Google Reader up as perfection but the fact of the matter is that the search function in GR could only find the post I was looking for about 70% of the time. (And that only reflects the times that I knew for a fact that GR was not finding the relevant posts). And remember, Google Reader had a search function that was built by Google, and even the experts at Google didn't always get it right.
And if Google can't get it right then what hope does their smaller competition have of achieving the impossible?