Shapes not clean when bringing into GIMP from inkscape

[Hai-Etlik]

It's because it's applying antialiasing where the edges of the shapes don't align with the pixel boundaries and you are zooming in so you can see it. The exact same thing happens when Inkscape is displaying the image on your screen. Zoom in on that screenshot from Inkscape and you'll see it there.

You should only worry about things that are a problem when viewed at the size you intend for it to be viewed. Antialiasing is normally an improvement when viewed at an appropriate size. Zooming in and looking for problems you couldn't have seen otherwise is one of the biggest time wasting traps you can find yourself in. You should zoom in to get a better idea how to fix the problems you CAN see at standard zoom, and that's it.

If you really need pixel perfect alignment, it's possible in inkscape by using a grid that's aligned to the pixel grid. You probably want one that's twice the frequency of the pixels so you can align shapes to pixel boundaries, and pixel wide lines to the centres of pixels. That said, you are probably better off with GIMP if you do need this.