Who Sees Ads For WPMU

The following quote form your product page:

This plugin takes an immense amount of work to keep this operational and working just fine for WPMU - which is why it's here, we'll be donating a bug chunk of membership fees to Ozh as a result.

Implies and reads to me that its incredibly hard to keep it working with WPMU and as such would put me off using it.

I'm sure you mean something else, perhaps the original plugin is hard and your version takes the pain out of it?