Edit: Ran into a thing to bee careful about.
#1 Use smudges in on layer on a multi layer PDN.
#2 Pres OK
#3 Go to a deferent layer and hit ctrl+f.
This makes the smudge effect SUBSTITUDE the original layer with a copy of the layer from # 1 and #2.
Not a bug, but something to be aware about.
This plugin does NOT work properly with Effects > Repeat x or [Ctrl]+[F]. I do not intend to fix this - ever - so don't even ask about it.
PS: Isn't this plugin also from GIMP?
The GIMP has a Smudge tool built-in, and I used the icon from that. The code is all original, though. GIMP source code is a nightmare.
Is it possible for plugins to have PDN shortcut keys like "Ctrl+Mouse wheel=Zoom in and out" & "Shift+mouse wheel= Pan left and right"?
It already supports the brush-size shortcuts, so there's no reason I can't expand on that and follow even more of the shortcuts, sure.
And there is a bug? (kinda)
When using smudge on an object with a transparent background. It will treat the transparent part as black.
I didn't want to deal with alpha values in the first release. For now it just ignores them. It will be fixed soon.
However, I get massive performance issues when using it with larger pictures (above ~ 1000x800 px). It tooks a while until the smudge effect is rendered, what drastically reduces usability (you have to wait 1,2 seconds until you see what you've done). Also the CPU goes crazy. I never had such problems with GIMP. Smaller pictures (e.g. 640x480) work fine with the plugin.
In my opinion it needs performance tweaks. (Indeed, I have no dual-core.)
Performance tweaks on the way!
In my tests the missing undo-ability was also a problem.
Undo on the way!
And maybe - maybe - future releases of this plugin should go in "Blurs". The reason for this idea is mainly the rather empty Blur menu compared with the overcrowded Distort menu.
Indeed. I'll consider it.
However, no one can doubt that this plugin is a great addition to Paint.NET and hopefully goes to the tool window for 4.xx. 
Rick and I discussed this briefly a while ago. Once I get the performance better on single-core systems, we can start really discussing it.
Oh btw, is there going to be a panel like in photoshop where we canadjust scattering, dynamics, size, spacing, texture? That'd make me leave photoshop for good, btw.
I don't know what those do. I'll have to get my hands on a copy of Photoshop so I can play with it. But yeah, bringing this Smudge tool on par with others like GIMP and Photoshop is definitely a goal I'm willing to work for.
Download from my plugin set 
that's just amazing 
