MSXML4 compatability problems?

[chiph]

We're looking at switching to MSXML4 for our parser (so we can use XSDs). But we've got a lot of existing code written against the 3.0 parser (Dim objDom As MSXML2.DOMDocument30, etc.). A concern is that the 4.0 parser replaces the 3.0 parser (doesn't run side-by-side).

Has anyone else made the switch, and if so, have you had any issues with backwards-compatability?

Thanks in advance.
Chip H.