1- Correctness. It's still possible to generate bad XML. Especially in 2 safe mode, checks on processing instructions, comments and DOCTYPE 3 declarations should be rigorously matched against the spec. 4 5- Control over presentation. How much is too much? Entities vs. CDATA, 6 placement of namespace declarations, whitespace. How much control 7 should the user be given? 8 9- Performance. Reducing the use of closures may speed things up, and 10 benchmarking would show whether or not it's worth it. 11