Good luck with the marathon Speedie. I have never tried not tapering, so I couldn't say for definite whether it works for me, but it seems to.
It makes sense that it should - the body has a chance to recover from the hard work, the muscles to repair themselves and get stronger, and for the body to lay down the glycogen reserves. You need some running to keep up the flexibility and speed, to prevent any loss of fitness, and for the psycholgical benefits - to believe you can still do it and to stop yourself going mad!
A few years ago the advice was do your longest run 2 weeks before the marathon, and then cut down mileage very significantly. These days, most marathon schedules seem to say do the longest run 3 weeks before the marathon, and then cut your weekly mileage by a third, and then by a half from your peak. The long run pattern may be something like 20m 3 weeks before, 16 m 2 weeks before, 12m 1 week before.
This pattern works well for me except I have more rest days in the final week, and end up raring to go.
One thing I have noticed, during the tapering phase everyone seems to have at least one run where they feel terrible. Don't know, could it be the body laying down glycogen so you feel very heavy?
