Yes, I actually have ;) I am a founder of a browser company. Our team is building a browser from scracth, minus the rendering engine for which we have chosen WebKit. Many of our beta testers have already indicated that our browser (Orion) is same or better than Safari, Chrome or Firefox. Hence, I believe it can be done and we'd welcome more formidable competition from Firefox in order to take on Chrom(e/ium ) clones that took over the web.