Hans, I've had the nik Color Effect Pro 2 "plug-ins" for some time. I agree they are a lot of fun. While you're at it, try experimenting with some partial filter use where you apply an effect to one part of an image and not another.
I like the drama in the skies you've created in the second image. The image seems a bit noisy though. Was this you intent?
I have it myself. I enjoy it. The Pro Contrast filter really makes adjustments painless. Since the D2X doesn't take UV shots really well, i'm experimenting with the best exposure to use the UV filter plugin.