Ditto. I'd like to see some side-by-side comparisons with PNGOUT, PNGCrush, OptiPNG, and AdvPNG. I use ImageOptim on my Mac to automate my PNG optimization—and it can get some impressive gains.
On the Mac I use ImageAlpha to reduce the colours to 256 (it has a preview window so you can see if it's OK), then when saving the file I choose the option to send it to ImageOptim.
On Linux you can get the same by using pngquant, then using trimage. AFAIK there's no GUI frontend for pngquant so I guess how many colours would be ok and check before running trimage.
The reason why I use 2 tools is that ImageAlpha/pngquant is lossy and ImageOptim/trimage is lossless.
The tools you mention use lossless compression. For 24-bit PNG files that means they probably won't come close the kind of lossy compression used by TinyPNG.
