Not a bug, just a problem...

I am making a filter than takes a single picture with a transparent background and makes a wallpaper that is seamlessly tiled. Simply enough I just offset the original image 8 times and blend all the offsets together. However, simply offsetting and blending 8 times takes more time than some of my surfaced filters.

Should it take that long to offset and blend? Aren't those two of the fastest components in FF?

Attaching filter here (or sending a link via contact for or even private developer's e-mail if you wouldn't like to disclose the filter itself) would be a good start to finding out why your specific filter is too slow

Hmm. The filter you provided renders in about 1 second on my machine with the current publicly available version (and in around 0.6 seconds using the internal performance-tuned build) -- I don't see any performance problems with it.

Maybe you're using a large input image? The rendering time usually increases proportionally to the area of the image (i.e. total pixel count), so if you specify image that is 2x larger than the original on both axes, rendering time will go up 4 times.

Also, are you applying the filter from within Photoshop (or any other host application) or from a standalone application? If it's the host application, I would like to ask you to test it from a standalone application, having the same image as input and tell me the performance difference if any, since the problem might lie in the host-to-FF interaction code, not in the rendering path.