I highly recommend that if we make any move towards this, that the software show verification in both/all units.

For instance, there should be 3 input fields, one for "BTC", one for "mBTC" one for "uBTC".  As the user enters a value in one of the fields, it would automatically update the other fields with the converted value as they type.  This makes it really difficult to get it wrong... if you're typing "10" into the BTC field, thinking it's mBTC, you'll see 10,000 mBTC showing up in the other box as you type.  Similarly, it should display all units on all verification windows.  Users may also use it for sanity checking conversion between units.