Very often I just need a normalized version of my vector that I know isn't zero-length.
Before I migrated to OpenTK I was using a LinearMath library that had a nifty little .Normalized property that simply just returned a copy of the vector but normalized.
Otherwise I manually have to create a copy, normalize it and use it. It takes two more lines and clutters the code.
For OpenTK you could add .Normalized and .NormalizedFast
What do you think? It is very quick and easy to add.