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I want to make a scene where someone sees a reflection in mirrored glass but I want the reflections to look like real windows so I don't want to just use a plane. They have to have some distortion. Every piece of glass has a particular imperfection so I don't want a global distortion it has to have a particular distortion for each pane.
How can I procedurally make a wall of windows but each window has a specific reflective imperfection?
If each window is a separate face you can unwrap with the Lightmap Pack method, scale down all the faces in the UV Editor with the Individual Origins Pivot Point selected, then in the Material use the Texture Coordinate UV output and give it a Musgrave Texture as Bump:
You can try it with this shader setup:
Just change the noise texture values to change the effect.
You can also try to add seams at the edge of your windows surfaces and then pack UV's with different methods/parameters so it will break the consistency of the "wobble" effect across the whole surface.
Examples:
A (maybe too elaborate, 'classical') pure-procedural approach might be to split your texture-space into tiles, using a Wrap node:
Below: original UV on the left. Wrapped UV ('Cell UV') in the middle. If you subtract the 'Cell UV' from the original UV, you get an index-per-cell ('idx'). 'Idx' is the coordinate of the origin of each cell's 'Cell UV'.
Once you have a per-cell index, you can use it for per-cell effects. Here it's used to give a random tilt per cell...
.. by looking up a bit of per-cell noise, and adding a multiple of it to the original normal. Below, showing 0, and increasing values in the Scale node:
You can also use the index for a shift of the coordinates of, say, a Musgrave texture, to use in a Bump, to put a wobble into the normals, per cell:
This shows 0 to increasing values in the 'Distance' field of the Bump node
If you combine the effects, you get a tilt-and-wobble per pane of glass:
This .blend includes the cluster for putting the black frame around the panes.
I would look at the window object rather than the window material or Texture, although all might offer an opportunity to introduce imperfections/waviness. For an object, look at the plane or and Wave modifier. Try a wave modifier with a Speed=0 (no animation). If using a Plane for the window, then also consider adding the Solidify modifier.
Here is an example, where I subdivided the plane, added X and Y coord waviness, and also added a Solidify, images are from the 3d View and Cycles Render (shows a building facade reflection), respectively.
Here is the example 
file.
BTW: Bravo to some of the other solutions involving materials. Those solutions might make for smaller files as there is no sub-division surfacing required.
