I've also read good things of Ko Cao Line: a saddle is a saddle, whether it's for a horse or a bike.
Either way don't waste your money on Proofhide: it's no better or worse than other dubbin, but there is no magic ingredient, just some rampant brand profiteering.
Don't be tempted to slather whatever you use on: the only times I have read of leather saddles being ruined, it is either i) becoming soaking wet and not shaped as they dry, or ii) over use of dubbin. It helps with absorption if the saddle is in a warm environment: a thin application, completely rubbed in.
If you don't already know it, the Audaxer's rule of thumb is "once a day for a week, once week for a month, once a month for a year and once year for life".