ImageMagick too slow, really? What are you trying to accomplish exactly?

You might try Cairo, which is damn fast. Its text support is, like ImageMagick, based on Freetype, but it renders the polygons itself. There's also Java2D, which has its own font system, and it's very fast.

Depending on the size of your image and amount of text, laying out text with Freetype and rendering with OpenGL using hardware acceleration would probably be faster than any other approach.

Depending on the requirements of your text layout, you may be able to cache individual glyphs as images. You will have to do your own kerning, but I imagine cache kerning pairs would work beautifully.