Crossfit might kill you, but as a user there's no practical downside to ad blocking. Faster web? Less chance of malware? Less annoyance? Heck, a product marketed as doing all of those things could probably be sold all on its own if not for the meta-irony of an ad for an ad blocker.

Seriously though, this is a good thing. Everybody needs to know about and install one. It should be considered a part of basic internet literacy.