I've never seen anyone mention the use of a screen magnifier to help them see the preview window of PhotoShop filters in particular. (Everyone's always used them, right? --and it's taken me this long to realize the obvious? )
In case everyone hasn't, I found "Lens v0.9" at Snapfiles. It magnifies the area around your pointer/cursor; you control the degree of magnification. What's great about it is that you can adjust the size of the area it magnifies, and you can also lock it in place--right over the preview window--and you can also set its refresh rate to be fast enough that you can actually see the results of what you're doing with the filter's sliders as you're doing it. (It can measure distances inside its viewing area, too.) It's only 64kb, and freeware.
The screenshot shows: top left, the image I was working on; bottom, the UI of Richard Rosenman's 'Pinocchio' plugin; top right, the plugin's preview pane magnified.
Magnifying the preview window of many older PhotoShop filters 4X gives the filters new life!