Power users are certainly valuable for spreading the word but it's only one way, you can also actually advertise and market the thing like Google did. And even though power users can spread the word, you still need a superior product for casuals to actually win them over. How long has HN and other forums been beating the drum for Firefox now? Has it actually made a difference in their declining marketshare (at least for desktop, not sure about mobile)?
I don't think it has, and I don't think it ever will. If Firefox survives and resurges in popularity, it will be for a better, more polished, more optimized, slicker product for casuals. And many power users will hate them for it. Well, that's just my prediction.