Hello!
I am demoing PL13 now. Here are my impressions. I can be wrong about some things, because I have yet to explore this application thoroughly.
User level: intermediate (I hope) amateur.
1. Boy, this application looks outdated! They could really make buttons flat, because these ones are simply obtrusive. And a set of icons not looking like straight from Windows 3.11 would surely be nice! Bonus point for enabling mono interface.
2. Open window- no EXIF preview. In browser OK, except that values should be highlighted red, not value names! RAW importer- no fast way to magnify to 1:1 and back

3. Toolbox- I really prefer "click once to display avaliable tools, click again to select tool" paradigm.
4. Preview of font typefaces in font selection combo, no problem with entering national characters. Bonus point here.
5. Help- missing icon before text "The picture file is write-protected."
6. What is HIS color space? Google knows nothing about it, neither does help (in practice)! And it's even in unsharp mask dialog!
7. In dialogs- no easy way to skip between 100% and fit to window magnification! Or am I missing something?
8. Why Levels is called Histogram correction???
9. WHERE IS CURVES? Help says to double-click curve field. I cannot find it, probably user error here. But WHY IT IS NOT IN A MENU???
10. Tool, Filter, Effects menus. I try to guess what they contain without looking inside. I pretty well succeed. Bonus point here.
11. Lightning effect- this is supposed to be a joke, right? Should be called "Branching lines". Does not look like any lightning I've seen.
12. Lights- step in a good direction. Now look at Picture Publisher's 8+ (RIP) Lighting Studio to learn how it should look like.
13. No gradient fills of texture fills? Bad.
14. As for sub-pixel unsharp masking (some user asked about), a quote: "Photoshop doesn't carry out any operations on 0.4 of a pixel -- the pixel is indeed the fundamental particle in digital imaging -- it just uses the sub-pixel values to decide how much weight to give to the surrounding pixels." So, does PL support sub-pixel radius in USM all in all? I would be also nice to see it in Highpass or Gaussian blur.
15. Drawing filter- preview is displayed for the whole image, not the selection it is applied to. Not resizeable dialog box- bad

16. Why Effect dialog boxes are not resizeable and Filter are? "Resizeability" item in lower right dialog corner would be nice.[/b]