The best thing that Firefox had going for it was that it was fast in comparison to the very bloated Internet Explorer. However, Firefox has itself become bloated, I think. I don't care much for Firefox or Chrome, my first choice in a browser being Safari, and my second choice being Opera. Nevertheless, being the default search engine in Firefox can't hurt, although there is some truth to the argument that anyone capable of switching their default browser to Firefox to begin with is probably someone who will have no trouble switching their default search engine if they wish. Still, most people will probably use it a few times before doing so and, if Yahoo is giving good results, may not bother. It's been a while since I've used Yahoo though, so I don't know how good the results are. Personally, if I am going to use a search engine powered by Bing, I'll use Bing since they give me gift cards and Yahoo doesn't.