What do you think about .Net only versions of APIs?

We have .Net versions of APIs and we have native (C/C++) versions of APIs.  There are cases where we have a native version, but we don't have a .Net counterpart.  There aren't any real cases where we have a .Net API, and no native counterpart.  What if there were?

Maybe we are already doing this to some point.  For example, if you want to send an SMS using native code, it can take about 15 to 20 lines of code.  Using the .Net SmsMessage class (in the Microsoft.WindowsMobile.PocketOutlook namespace), you can code it in 2 lines! (1 line if you want to sacrifice a little bit of readability, but not much). 

Would not having a native version be a big deal?  What types APIs would you be ok with a .Net only version, if any?

- Brian