This plugins works great...if you can get the scripts to install properly.
I installed it on one server and it works perfectly. I cannot for the life of me get it work on my second one.
I've tried all the possible options, installation instructions and work around's...still nothing. I will say the install instructions are not easily accessible...at least for pngcrush.
What are the exact commands that you used to set it up on your systems? The commands I used on one server doesn't work on the other and there identical.