There are many seats out there that do a great job for XC riders, triatheletes, etc. Seat position is KEY for many different reasons, I don't need to go into them.
I was involved with a saddle design that my brother-in-law came up with the concept for a few years ago and during that time, I learned many things about saddle position, design, comfort, etc. We were working with Selle Italia on a few of the saddles and they were awsome (see the website www.koobi.com
). When my brother-in-law asked me to help out re-designing the seat and helping out w/ new products, I jumped at the opportunity. After a lot of R&D and riding, we finally ended up with a great saddle line.
Anyway, everyone is going to have their own way of riding and their own preference as to materials (gel, foam firmness, etc.) and the position of their saddle.
For XC riders, they tend to position the saddle with the nose pointed slightly downward and depending on the frame geometry, the seat will need to either be slid forward or backwards depending on the rider. IF YOU HAVE A SEAT THAT UTILIZES TITANIM RAILS, BE SURE TO STAY WITHIN THE SPECIFIED LIMITS OF THE SEAT FRAMERAIL (painted on the side) OR ELSE YOU MAY BE IN FOR A SUPRISE. Titanuim is great for weight, etc., but is a brittle metal as well and can shatter if not installed correctly.
Downhillers keep their seats pointed up and seatposts low because they catch air and they need the room to jump, etc. and so the seatpost doesn't lodge itself where it doesn't belong.
Since they are mostly going downhill, they keep it up also to keep them on the level, not sliding on the saddle.
If you would like to know more about positioning saddles, etc., feel free to PM or email me and I can pass onto you what the guys from Selle Italia told me regarding saddle setup, etc.