Special Characters window no longer resizable in OS X Lion
You can resize the window, but it's different than most windows in Lion.

If you click and drag a corner or an edge, the window will resize. Yes, it doesn't look like you can use the corners, but they do work.
This appears to work with every corner except the top left, which is blocked by the close button. Edit: Actually, if you aim just right (to the top left of the close button) you can use that corner too.

To summarize: Things still work, but the active areas are tiny. You just have to be careful.

This behavior is strange, and seems buggy to me. I expect than a future update will fix this and allow you to resize by all the corners and edges.