Well, after the UI replacement, enhanced magic system + spell-making (hopefully), new lore-friendly creatures, hand-placed loot, skills/weapons/armor and everything balance, and complete texture replacement, I'll be ready for the "luxury" mods, such as quests and hopefully head/face generation improvements.
Actually, at the moment one of my big grievances is sorting, particularly potion sorting. I can't wait to be able to open the CK myself, and to reap the benefits of the modding community.