I've been having a lot of trouble with the combobox's rendering under IE6 - rather than appearing inline(well, "relative"), it acts as if it is position:fixed, and stays on the screen even as the rest of the content scrolls.
The combo is inside a table in a borderlayout (actually, inside a nestedlayout inside a borderlayout.) Normally, within that region it'd also be inside a floated div, but I've tested without any personal stylesheets and it's still happening.
When I do use my stylesheet, the float around the combo combined with some other CSS causes the trigger button to wrap to the line below the text entry box.
I realize the combo is a new control, and just hope that it'll get some attention in the next alpha!