Hand-written SVG, treated as elements of the markup (rather than an external black-box object or image), usually works well. It's easily* styled, scripted, and has good clean structure and values. There are, however, a couple of problems.

Hand-writing a complex graphic is difficult! (ex: editing coastlines on a map) Unfortunately, current WYSIWYG editors produce bloated, illogical output full of bizarre measurement schemes, unnecessary translations, and incompatible proprietary garbage - sort of like the bad old days of Frontpage and Dreamweaver.

*There are also some quirks in both styling and scripting them (as others have mentioned, height is one, another is having to use NS versions of DOM functions instead of normal ones - but only sometimes).

Maybe by the time SVG turns 21, those things will be mostly sorted out. It's still in its awkward teenage years.