Easyrider:
In terms of that disc wheel thing. A front disc is very very very tough to control as long as there is any wind. Also understand that sponsors dictate oftentimes the exact equipment that a rider must use. Note however that sometimes you do still see dual discs: Cipo and Danilo Di Luca were doing it in last years Giro.
Note: On outdoor velodromes (where there is wind) Pursuit riders will never use a front disc, only a rear. On indoor velodromes (no wind) all Pursuit riders will adopt dual discs. Since there is obviously no climbing in a Pursuit track race, the issue here is obviously the negative handling characteristics.
A lot of Pro's porbably realized that they were wasting more energy trying to keep their bikes going in the right direction to justify the aero advantage they got. I doubt it was ever an issue of weight. Corima and Zipp discs are around 900 grams, which is light to the point of no excuses on the climbs.
- Maurizio