Nagamasa...why don't you make the contact search bar transparent, as the contact list??
You can find how to do that here:
http://shoutbox.menthix.net/showthread.php?tid=80913
You could also add boolvals to make transparent an option...I don't think everyone would like their contacts lists always transparent.
Hmmm...and try also to hide the tabs separators, they look a bit ugly.
Keep up the good work.