zerorepent

It is relatively easy to use gwen gui, there are samples included for several different rendering frameworks, opengl, direct2d, Allegro, SFML etc. (It takes som tinkering making direct2d work with directx but there exist some good tutorials on how to do it). 

wasteful might have been a poor choice of words, but what I mean is that since I'm not using complex pattern, i.e. just filling with zero using fill seems a bit overkill.

The Buffer sizes is in ranges between ~64KB and ~128MB. Using a small pattern a float seems to be rather inefficient because even if it zero:ed it still need to do size/4 memcopies. Thats why I thought maybe using unmap/map and memset might be faster, I guess my best option is to time it and compare. (or something similar to that)

Actually this was one of the greatest dissapointments for me after buying a MBP. Before buying I just looked at the hardware and not into further details about drivers  

I think the easiest way is to keep the vertices in mainmemory and then make the update against that and send the updated relevant parts via map/updatesubresource with write discard as MJP wrote below.

Thanks! It works perfectly for the Id3d11Device1, but fails on the id3d11devicecontext1. I guess thats because I use featurelevel 11 and not 11.1 so I don't think thats an issue ^^.