In the epic game (normal civ) it does nothing (or virtually nothing). It doesn't provide any new attributes / units / improvements. It does add points to your score, but it is so slight as to be almost nonexistent -- adding one or two specialists or happy citizens to a single city adds more to your overall score than discovering a future tech does, IIRC.
The same may not be true in a Conquests scenario, and may not be true for a scenario with different scoring / victory methods (like victory points?). I suppose in C3C you might be able to generate a scientific great leader by researching a future tech (is it possible?), but I can't see how that would matter since all wonders are gone, you don't need a boost to science research, and rshing normal improvements is probably not a priority if you've reached the point of researching future techs.
Catt
