Although it's not as good as the real thing, I have found it invaluable in keeping me going when I otherwise might have stopped.
You need to get into a turbo mindset and break it down into say 5 minute groupings. So for 5 mins you warm up, then gear change and do another 5. Then the next 5 at a faster cadence or HR, then steady, then 5 fast etc... If you do this the time passes quicker. Music and DVD/channel 4/BBC downloads are what I use but they are more background and once I get to the end I've got my head down and my teeth gritted in an effort to keep the same cadence/speed, that's my method anyway but I still can't manage more than an hour.