I just started diving into WPF. First thing I noticed and which I really hate is the ugly rendering.
I don’t know why but for example borders or lines turning ugly sometimes.
Take a look at the Screenshot. The bottom line is ugly. Not that crisp like the centered line.
Any suggestions to make that better?

See the second answer of this SO question
which suggests using UseLayoutRounding=False in preference to SnapsToDevicePixels.
As an aside if you’re using bitmaps then RenderOptions.BitmapScalingMode can be useful (from this SO question