the other bug is not really a bug, at least as I am aware - it's the "good old" feature - when receiving call from some contact from Your black list - sound, and visual notification appears, but only for an instance... it varies from one tenth of a second upto to two seconds... that "feature" was also in all of the symbian apps - it has something to do with the OS - incoming call just triggers the notifications before any app could react and prevent it... let's hope that Inception will ease the solution of this one...
EDIT: and yes - the other side receives the busy tome immediately, unlike on all the other apps of that kind on symbians, when the other side had been receiving tone or two of the normal waiting tone...