Since version 1.0 I used pixelmator (PM) as "externel editor" for my photos in apples aperture.
Pixelmator is a lightweight and cheep (50,- €) photoshop alternativ - and it worked great until version 1.5 (code name "spider") was released early september. Since 1.5 PM can no longer be used as external editor for aperture (or iPhoto).

I could switch back to version 1.4 but that version does not work in snow leopard.
So I had to decide either to downgrade to Mac OS 1.5 and use PM 1.4 or to find an alternative for PM.

I asked the PM team to fix the problem in their forum. No response.
I asked the same via mail. No response.
I bagged to release a patched 1.5.1. No response.

The PM team seems to be on an very long holiday trip ...

As a photog I had to make a decision. I ordered the NIK-Software-plugins for aperture today and do not longer use PM for photo editing from now on.

The easiest way to loose lucky cutomers ist to release a buggy version and take some month off.

UPDATE (Oct. 2010):
About one year later they released version 1.6.1 and fixed this save-back-to-editor-bug. However I am so lucky with the NIK plugins that I stay with NIK.