I love the set stages though I've always wanted a stage editor in Smash Bros. I reached points in the hundreds of hours I spent playing both the original and Melee where I just got plain bored of the stages and characters. I'm a value whore so I'm always up for more stuff. Even though I'm terribly skeptical of the idea of customizable characters in Smash Bros., I'm totally open to the idea though I doubt they'd put it in if it didn't work.
And, as a value whore, I really would like to see all the older stages remade for Brawl. The more options and additions there are the better. It took years of playing nearly everyday to get tired of the other Smash games, but I did get tired of them. Melee is almost unplayable to me now though admittedly due primarily to Brawl's sheer awesomeness. I almost feel like Sakurai and his team set the bar so high that the expectations for this game are unattainable and that I'll find myself disappointed in something. For instance, the introduction of 3rd party characters has spoiled me. I'll probably always think in the back of my mind how much more awesome the game could have been with character X or Y.
It won't ruin the experience or come close but hype is almost universally a bad thing. I can't remember the last game I was super-hyped about that actually lived up to all my expectations. The original Metroid Prime was close and without thinking too hard about it, MP was probably the closest it ever got.