I've tested some of my SVG demos with FF 3 and they run much faster than with FF 2 (I think that's due to Cairo being integrated into Firefox 3). Opera and Safari are very fast compared to FF 2, too.
As for feature completeness I agree with you. The Firefox SVG team is very small and not funded by the Mozilla corporation (at least that was the case last year when I talked to one of its members) - the SVG standard, on the other hand, is HUGE.
I'm using it for a simple web app, testing in FF2/FF3/Safari, seems to work fine... there are some annoying bugs in the implementation (the kind that have been open for years), and inconsistencies between Safari and FF, but nothing I couldn't work around so far.
We started by using graphviz to generate svg, but then couldn't find any decent in-line svg viewers. Do you know of any non-java applet inline svg viewers?
Have you played with SVG?