The only solid vector graphics app I’ve used in open source is Inkscape. I agree, it’s very difficult to get to know, even moreso if you’re coming from old school raster imaging and don’t get all the mathiness. I had to learn Inkscape though, because I needed to make fantasy maps with textual titles that didn’t look like crap when rescaled.

I’m no expert, but it does pay off to learn. It’s a very powerful set of tools.