The spells, for the most part, look fine to me. I like the fact that with mirror image, there's no wrangling about whether if an attack missed, it missed narrowly enough to hit an image, or which exact image did it hit or anything. The spell is simplified, and that's they way I like it. There's no math about figuring out the mirror image's AC, and no figuring out, every time you hit, the odds of how likely it is that you'll hit either the wizard or one of his 6 images. Plus, as people have mentioned, mirror image was sort of ridiculously powerful, basically at any level. Anything which drives the miss chance above the miss chance for full concealment or invisibility is silly, in my book. This things reasonable and simple. There's no extra rolling, which is great. Plus, think of it this way. If an enemy needs to roll a 13 to hit the wizard before the wizards casts mirror image, then the wizard has just made himself 1/4 as likely to get hit. Voila.
That said, I would personally like it better if only misses which targeted AC destroyed an image.
I like the Displacement spell too. I like that it's an encounter power that works on anyone. It makes the wizard helpful to the rest of the party, or at least whoever's getting hit really bad. Gameplay-wise, I think that it will usually work out that the wizard only uses the power whenever the results of a reroll couldn't possibly be any worse, like when the target is getting critically hit, or it's a life-or-death situation.
Like most of you, I'm surprised at how high-level all the spells are, but this is something that I'd like to evaluate in some context, not just what level the spells "always were".