Xycraft, yes, mystcraft, no. Mystcraft and ars magica have some kind of server-side incompatibility. Oh, and some crafting stuffs should be fixed next update. I'll set up some admin trade-o-mats at spawn for uncraftable items. Due to thaumcraft aura changes, the map may need to be reset, but I won't release the ModPack update until there's enough changed stuff to warrant it.