Apple is in a very strong position, they have an amazing product that people will literally
line up to buy. What they don't have is a lock on the market, though, and they know it. They either innovate, keep pushing themselves, or they'll end up steamrollered by someone else.
Remember that in 1995 people did line up to buy Windows 95 and while future launches weren't met with as much fanfare, people would actively seek out computers with Windows on it and had no time for side-show attractions like MacOS or Linux.
Amazing how that can come collapsing down just because of a few mis-steps. You have Vista, you have a near decade of focusing aggressively on the server market and leaving the consumer side to twist in the wind, neglecting their important and dominant Internet Explorer product for the better part of six years.
In other words, Apple is just one Steve Ballmer away from total irrelevance.
The company best situated to take down Apple doesn't exist yet, not in the form it will ultimately be. Maybe Samsung will finally go beyond emulating and will build their own platform that resonates with consumers as well as they'd have you believe in the marketing... Maybe Microsoft will hire new leadership and straighten out the train-wreck that Windows Phone 7 is...
As much as Apple is doing a great job, it's frustrating when there really isn't any competition. We need a market where there are two or three very good choices.
Like Xbox 360 or PS3 or Wii where each have their merits. What will the world be like if that's reduced to just one?