As an oldschool RPG and Might and Magic fan, this double entry was more than I ever hoped for. Too much, actually.
The idea of using one party to complete both games back-to-back seemed great. I enjoyed Clouds of Xeen a lot, and was looking forward to the second game.
But by the time I finally crossed over to the Darkside, I was tired of the mechanics and ready to move on to a different game. Maybe I just lacked the patience back then, YMMV.