Sure there are reasonable competitors. Yes apple has the simple to use dummy user experience down pat. But the new google phone shoudl compete quite nicely and even windows mobile (with some heavy mods) can actually be better than the iPhone.
For computers there’s really no comparison. PC is the way to go whether you go with windows or Linux.
And the iPad is easily beat by netbooks.
So while there is always give and take when changing vendors if it really bothered you enough...I’m sure you could find an alternative.
Now if you said their isn’t a viable alternative to Microsoft then you may have something because nearly everyone has to deal with them at work and they have been deemed a monopoly. But even that is changing now.
I guess the you could say you don’t like your cable company, but then there’s satelite TV. Well I guess you could say you don’t like your government...then you are stuck.