Don't know what do you mean, 'cause I'm working with Cubase VST expression and since 6.0 it works great! If something goes wrong it can be easily a misstake by yourself, the Cubase manual doesn't explain the workflow very well (and the possibilities of source of errors). You have to be very careful building up your customized expression maps. But one's correctly done it's a revolutionary (and since 6.0 a steady working) feature.
Best
Frank