An important part is that Inkscape's UI is based off CorelDRAW, somehow* a popular vector program. This one works very similar to Illustrator's, and that's probably the most commonly used vector program. This being a free alternative is nice. If you're wondering what you're missing out on since it says, "trial" in the FAQ:
What’s the difference between the free and paid versions of Expression Web and Design?*Its UI sucks.
The features and functionality are the same between the free download and paid versions. The key difference is that the free versions are not supported, meaning they come as-is and no Microsoft technical support is available (these products are supported via the community).