It would seem from their quarterly profit that selling free software is even better.
We have 400 servers I manage at my site, and it is only one of many sites we have. Most are Solaris and HP-UX with a good dash of Windows. The difficulties in migrating are centered around logistics, software, and customer relations. We, like similar companies of our type, deal in huge amounts of financial transactions so switching to Linux has been slowed while growth and stabalization was watched. I think many companies can now look to the successes of other business and say 'it works' - which will alleviate the concerns of those higher up and the customers we deal with.
Thanks to the pioneering of those with the guts to switch I forsee many larger companies now willing to see it as a viable and stable switch. Concerns and worries can now be addressed with case studies and general market analysis (for those higher up who would ask, will they be there in 5 years or are we going to need to switch back, what about growth of product, etc). Linux is at a prime time to push into the market deeper - but contrary to what some say Microsoft will continue to have a sizeable market share and .net is going to grow.
In 5 years the market will probably be linux and microsoft with a spattering of solaris, et al. Both linux and MS have their specialized areas which will continue to draw techies to them.