What I have learned about Inkscape
Always remember that the computer sees things you don't - eg. the vector lines under a fill or picture.
If the file is huge and has lots and lots and lots of nodes, exporting it to pdf can be a hassle.
Sometimes when things aren't working for some mysterious reason, ungrouping objects and/or breaking the paths apart fixes things.
When importing Adobe Illustrator files, you should check if automatic scaling is on.