Hi,
There are certainly enough SVG compliance issues to fill a GSOC. As Jasper mentions Markers and linearRGB are two items but there are many more. Here is a quick list:
* Filters: Use of linearRGB. Use of primitiveFilterUnits (also add GUI). GUI for feImage's preserveAspectRatio. feTile. Fill Paint/Stroke Paint inputs. Many minor issues. (A good GSOC project would be to focus on filters with the addition of speeding up rendering by parallel processing.)
* Markers: ViewBox. End of stroke.
* SVG Fonts
* Text Underlines. Alignment issues. Left to Right text. Vertical text. Many minor issues.
* Basics: Overflow: visible. Entities. Using ObjectBoundingBox for coordinates. Masks: Clip Rule. Square butts. Switch support. Namespaces. External SVG support. Many minor issues.
* CSS Inheritance issues. Font fallbacks. Many minor issues.
You can find a web page showing 0.48 results for the W3C SVG compliance tests at:
http://tavmjong.free.fr/INKSCAPE/W3C_SVG_1.1F2/harness/htmlInkscapeApproved/...
You can get a summary at:
http://dev.w3.org/SVG/profiles/1.1F2/test/status/implementation_matrix.html
Hovering over a "Fail" will usually tell you why Inkscape failed.
Tav