Heretic,
just a quick answer before the people from tekin chime in.
"Timing boost" is similar to what you used to adjust on brushed motors only done by electronic means rather than mechanically changing the position of the poles in the magnetic field (which is what you do when you turn the endbell around). Changing the position of a pole in the magnetic field means that the magnetic force that spins the rotor of your motor is going to come into action sooner (when you advance timing) or later when you retard it. There is more to it, but basically this is what happens.
The reason it is called timing boost is because theoretically it can give you more timing than it is available on your motor (physically). As it has been discussed here, going over 30degrees total timing (mechanical plus boost from hotwire plus the advance in motor sensor reading-this is inherent to sensor construction and I understand it is around 15 degrees) may actually hurt performance rather than help.
Hope this helps.