Oddly enough, the "X alternative" chart could be seen as a health metric, at least as much as "X" itself would be.

You could argue "if people are searching for alternatives to my service, that means they (1) care enough about a core aspect of my service that they're inclined to find an alternative rather than simply leave, and (2) other alternatives/competitors are not already obvious (market dominance)."

Of course that's a stretch, and if enough people really are dissatisfied with your service you stand to lose them to alternatives, but I guess the point is that google trends doesn't really imply a whole lot in this case because it's going to be biased by many things - including overall popularity.