It can only be a good thing if many more people and companies did look
at alternatives - it would encourage Microsoft to develop IE further
and have a plugin architecture like Firefox. One where you could extend
the browser by simply using XML, JavaScript and CSS in a sandbox mode -
no extra access rights to OS needed.
There is no reason why it isn't possible to do this kind of thing - you
can extend it using web services, RSS, Atom and any other technology
that works over standards HTTP. Just look at the extensions available
for Firefox and see how lightweight that browser is.
Good examples of extensions for Firefox are the
Web Developer toolbar (indispensible for Web Developers - there are no equivalents for IE that I am aware of) and the
Mozilla Amazon Browser (which you cannot do with IE at all).
I cannot see why IE cannot do things like this (without the use of
ActiveX) - if it could there would be massive potential - web
developers could make the user experience far better.
What would be good (but very unlikely to happen unfortunately) is
Microsoft to work with Mozilla / Opera to develop a cross-platform
standard. That way someone could design a site that is guarenteed to
function the same no matter what OS / browser they are using.