...which is a fine sentiment but does make sharing experiences more difficult - I would need your exact config file in order to reproduce your seed. For that reason it might be better to kep the potential for all biomes, but pick a seed that gives the biomes that you want nearby. Which also means that if you decide later on, "I want to visit a redwood forest", or "I forgot to include Small Jungles and now I want some Quicksand", you haven't cut off your options. You just need to travel.
If you remove some biomes in your config, can you still make a Mystcraft Age with that biome? Oh, the mechanics have changed now haven't they? So that makes two questions: In the old mechanics, could you still randomly find a non-config biome, and in the new mechanics can you still find a symbol for non-config biomes?
In actuality, to achieve the exact same experience from a given seed, you must preserve all hits on the random number generator, and their order...meaning that you must preserve the load order of mods, the version of mods and the configuration of mods. So...already, you must share more than a single seed. If you are not using modded terrain generation, these little differences are not really noticeable, but a mod like Extrabiomes amplifies the effect of small changes in a very visual way. The reality is that a seed no longer is enough to fully describe a gaming experience.
For the next major version of Extrabiomes we will be introducing some features that allow "terrain artists" to heavily influence the way terrain is generated. It is difficult to explain in this setting, but a good overview is here. These features will make config sharing an even bigger part of sharing worlds.
Regarding Mystcraft, as long as a biome has an id in the config file, whether it is disabled or not, Mystcraft will create a symbol for it.[DOUBLEPOST=1361462516][/DOUBLEPOST]
I agree completely. For me customization of the experience is the holy grail.But ultimately my thoughts are - "Customization is King". Let the Config file for ExtraBiomes let you determine how frequent, how much, how many, which biomes, etc, and your ills are cured. Every player using it can custom fit it to what they want.