Inkscape creates, converts, and edits images, applies filters and effects, and packs a host of brushes, stamps, templates, and tools. Inkscape can manage and modify layers, paths, and extensions, and its Help menu includes a manual, tutorials, FAQs, a Command Line option, and many more resources, not to mention the support and regular updates typical of open source projects.
Open source freeware: Developers and enthusiasts donate their time to keep Inkscape free and at the cutting edge of features and performance.
Layout: Inkscape's user interface has a familiar look, but it's not a Photoshop clone. For example, the scrolling spectral line (with color numbers) and axis display in the bottom panel not only set Inkscape's layout apart from Photoshop's but also improve upon it.
Extras: Inkscape has interesting features around every corner, like an XML Editor, input device configuration, and bitmap copies.
Not quite Photoshop: Inkscape is an impressive app that performs superbly, but it can't quite match Photoshop and similar software in features and extras.
Inkscape is a strong performer, packed with features and extras, supported by a dedicated community, and totally free.