I submit to you as an example Chrome, which while technically sound has not exactly caught fire, despite Google's ability to promote it from the Google page.
On our web sites Chrome has gained no share in the last six months, while Safari (due to iPhone's increased share) has surpassed FireFox.
This recent report, http://news.cnet.com/8301-30685_3-20001546-264.html, actually gives Chrome 6.1%.
I'm just saying given the engineering resources dedicated to it, and the unparalleled promotion resource available, it could do much better.
Personally, I use Chrome, but I object to the product management decision not to offer a dedicated multi search box like FF and IE. I think this was an engineering driven decision because the omnibox is so [fill in your favorite positive adjective].