Monopolies are ok if they are created and kept through legitimate means. And I think WebKit's monopoly on phones is legitimate and well deserved. If Microsoft put together a comparable engine (and it is very possible they have, I haven't tested it) then I would be happy that there is competition. But diversity for diversity's sake is not a good reason to not use WebKit. In fact it is very possible it would do more harm then good.

I am hoping* that Microsoft drops IE (the rendering engine not the browser), and throws it's support behind the Gecko engine. With Microsoft supporting Gecko, and Google and Apple supporting WebKit, we should see nice growth browser's capabilities.

*I know this won't happen, but who says a man can't dream.