According to the 2010 Embedded Market Study[1] the percentage of people who are not using Embedded GNU/Linux due to the lack of real-time capabilities went down from 25% in 2007 to 18% in 2010. I'll leave it up to you to interpret those numbers, but I strongly believe that it might be worth having a look at this subject.
Wat is real-time?
Real-time might, as the name implies, sometimes also be about timeliness (fast), but in my humble opinion it's usually about determinism. To be precise about event- and temporal determinism (event determinism meaning that you know the state of the outputs with a given set of inputs; temporal determinism meaning that you also know exactly the timing).
Coming back to real-time versus real fast - In case of an aircraft navigation system deadlines are in the tens of milliseconds, while for an airline reservation system the deadlines are at about 15 seconds.
To view the entire article go to
Getting real (time) about Embedded GNU/Linux