Thanks very much!
But I still don't understend, why update() doesn't notifiy GV about my changes. I used update() before (in my adjust method - only method when I'm doing items changes) and so I thought, that I'm notifying GV about changes. But in Qt 4.6 it's not right more. However in documentation for QGraphicsItem is still written:
Schedules a redraw of the area covered by rect in this item. You can call this function whenever your item needs to be redrawn, such as if it changes appearance or size. ....
If the only thing prepareGeometryChanges() does is calling update if necessarey, why I can't use update() instead? It was the reason I've called update() at the end of my adjust() method, to be sure that it will be called ever - maybe not good for performance ...

But I've just read this for QGraphicsItem::boundingRect():
f you want to change the item's bounding rectangle, you must first call prepareGeometryChange().
So I'm quite confused from it :-). Does update() need any other methods called before itsefl in order to GV realy update item on scene?

It's not so important since it's functionaly for me, but I'm interesting about it.
Once more thanks for replies!