I like Psion's list, because it saved me the trouble of having to think up all those really good answers. Give me a module that does those things, and I'll be pretty much drooling to run it.
Add in
Easy-to-use NPC descriptions, and I'm completely sold. Don't just give me a solid eight-line block of stuff like AC and attack bonus and leave it at that; put it in a format where I can almost immediately pick out all the important combat stats, the last-minute stuff you don't think about until you need it like grapple or trip bonuses, and what spells or spell-like abilities they have available without having to scan desperately for 'em in the middle of the fight. And if you really want to impress me, suggest what their strategy might be, so I don't suddenly realize four rounds in that the guy would've cast three defensive spells before entering the room, or that he would've
plane shifted out after he got nailed by the fighter for over half his hit points. I'll nearly always embellish and improvise on what I'm given, but being given more up front makes that so much easier and is really cool.
I'll also add that Psion's right when he praises the Banewarrens for adaptability; our GM is currently running our Scarred Lands party through it, and has commented more than once how easy it was to make it fit into that setting.
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so, basically, what i'm trying to say here is that psion wins
ryan