I have been playing with vector in krita recently. It's really fun and exciting, but I have face with one problem.
I'm mostly using Polyline tool for vector.
When I use Polyline tool in Normal/Paint layer, the brush size and color seem to match with the pen setting.
But when I use Polyline tool in Vector layer, the color works fine but the brush size/thickness is set to default value, like in my example it's (4.17).
It's really annoying for me because each time I want to draw new stroke it's set the size to default value

It is a some hidden setting that I missed or it's an unfinished feature?.
screenshot :

http://imgur.com/ZmFlFsd

Yes, this is something we fixed in 4.0 as part of the vector fixes. 4.0 is still in development though, so you'll have to deal with this oddity for now.

I guess that answers my thread. As a workaround,one should use Inkscape - enable pixel grid, and enable grid snapping. Doesn't really help for vector-based selection though. Krita is amazing tool for selecting non-organic objs in photos with vector and select opaque.