Really? Ask Wordstar, Wordperfect, Lotus 1-2-3, dBaseIII, Netscape, and countless other companies what fat lot of good the early lead did for them?
I'm no giant MS fan, but at the same time with most of these should serve as an example as to why if you're in the lead, you can't rest on your laurels. Stop innovating, and your product becomes inferior over time. Your competition will catch up (and with that momentum, quickly leave you in the dust). I stuck with Wordperfect, Lotus and Netscape for the longest time. I resisted, but eventually the realization came that something better has come along and everyone else has moved on already.
So I used IE for a while. Then Firefox came along. Et al, et al.