Which version of MSXML should I use?

Question

Seems like this would be a common question, though I could not find it on SO.

Which version of MSXML should I use in my applications, and more importantly,

Answer 1

I recently created a JS library that tried to degrade gracefully from the latest version to the oldest. I found that MSXML 3.0 is very well supported on most systems. I had wanted to use v. 6.0 when available, but it broke on some IE 8 installations. So, I had to change my code to try v 3.0 first and then v 6.0 and then v 2.0.