Adrenaline junkies and human drones.
If the altered perception of time doesn't actually impart enhanced thought processing, then all one is really doing is turning on or off their memory recording (or at least time temporal tagging of memories). It's a rather simple way to achieve the desired effect. To put it simply, if you can't think or do anything faster, then all that matters is your recollection because a single instant of slow or fast time is meaningless.
To slow down time people would be able to selectively activate tachypsychia. This is the phenomenon people experience in times of extreme stress, like a car accident. For people experiencing it, time seems to slow down. Of course, that's not what really going on. It appears what's really happening is people are simply more focused and remembering more of the event. It's like the replay for memories is always at 27 frames per second and in stressful times we record at 60 frames per second (making playback seem half speed).
This is also known as the oddball effect and was tested in an excellent example of what the life of a test subject can be like:
Research conducted by David Eagleman has suggested that time does not actually run in slow motion for a person during a life-threatening event, but, rather, it is only a retrospective assessment that brings that person to such a conclusion. To bring this into the realm of scientific study, he measured time perception during free-fall by strapping palm-top computers to subjects' wrists and having them perform psychophysical experiments as they fall. By measuring their speed of information intake, they concluded that participants do not obtain increased temporal resolution during the fall, but, instead, because their memories are more densely packed during a frightening situation, the event seems to have taken longer only in retrospect.
There is a less drastic effect known as chronostasis, most easily observed through the stopped clock illusion. You can try for yourself. If there is a clock in the room with you or a watch on your wrist with a seconds display, look at it and watch for the change in seconds. The first second appears to stretch significantly longer than the following seconds.
To speed up time people would simply record less information. You know the best way to make eight hours pass in seemingly no time? Go to sleep. Unconscious people don't experience the passage of time like they do while awake. The best way to do this while awake then is to be a drone, perform tasks on autopilot. Many people have experienced making the very routine drive home from work and realizing that they can't really recall any of it when they get home. They are paying attention, signaling, stopping at lights, but not committing the events to memory.
I'm not sure things would be all that different. Many people do this naturally a lot of the time. They can still learn things, be productive, and enjoy life. They might just have a harder time remembering when it was that they completed some task at work. They'll remember that they did it, but the temporal reference will be much more coarse (I finished it Tuesday, rather than I finished it about 3 o'clock on Tuesday).
It would certainly be an excellent skill to have and I believe it can be trained to some degree in people. But it won't topple society. I think it may make us more efficient, actually.