I expect others will respond with regard to the specific brecoflex treads they have used. While I encourage you to investigate the use of treads as an alternative -- they offer many opportunites -- I would suggest that reliability compared to a properly designed chain/wheel drive system might not be one of them.
While it is indeed frustrating to have chains come off in competition, that is an exceedingly rare event if the chains are properly tensioned and the sprockets are properly mounted. I believe there are some powerpoint presentations in this regard on the FIRST web site.
http://www.usfirst.org/community/frc...t.aspx?id=1108 might be a good place to start. I suspect you will find belts/treads to be at least as challenging as chain to align properly and get a reliable drive system.
That's not to say you shouldn't investigate treads... go for it... but consider that the vast majority of teams have chains and sprockets similar to those in the KOP and they work very reliably.
Jason