+1
Having Flat Keys and, especially, Flat Notes in the Key Editor is more than just a convince, it is essential.
The Chord Track and Chord Assistant have partial implementation of Flat Notes; the harmonic tools within Cubase are impressive and enjoyable to use, but not having the Flat Notes in the Key Editor and Flat Notes and Flat Keys throughout the program is a real, musical deficiency. 
I think better in Flat Notes and Flat Keys and really feel uncomfortable having to write a G Minor as G, A#, D (and so on and on). Help us, Cubase team, please! We really need this. Thank you.