And with the universal config project, huge props to the people involved with that, it's not too difficult even in 1.6.4. I'm running a server with a decidedly non-stock version of Monster and I had to fix - count it - one ID conflict.1.7 does away with Block IDs as far as the player is concerned. With that change, adding a mod becomes a 'drag-and-drop' exercise. You will only need to mess with config files if you want to change options or adjust the balance.
Not all mods will be compatible with all others. However, IDs were the biggest hurdle for most people in constructing a pack, and one of the most annoying things in the world to deal with.
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