In philanthropy, yes. His personal conduct appears to not be so admirable.

How important is that?

Considering that everyone has a chance to make personal decisions, but most people won't have the opportunity to make philanthropic decisions, can you see why the personal decisions someone makes are really the only thing important to get a measure of how good a role model they are.

It's very important in that by positioning his foundation as the largest global health provider in the world he could easily use it for nefarious or selfish means if he desired. It's very difficult to judge the motivation for Gates Foundation work on the foundation alone (for the same reason it's tough to judge the value of a VC-based startup by it's initial pricing scheme), so it's reasonable to look at his personal conduct to understand his motivations.

I for one, am not super happy that half of the third world relies on a child rapists' friend to get their Malaria vaccines.