A good reference:
MSDE Facts: "Despite how great MSDE is, I find myself constantly forgetting just what exactly its limitations are. So, without further ado, MSDE Facts:"
It's always a bit odd to me that SQL DBAs actually know very little about MSDE when it comes down to it. All they know is that on the last scan they performed for SQL Servers, twice as many MSDE installations popped up as databases.