Depending on the background you're using you may not even be able to notice it. Regardless of that or a potential glitch, the free program Glass2K will let you customize the taskbar's transparency, and that of entire windows as well if you so choose.
Hope this helps,
John
Hi,
I have Vista Ultimate and I am using the Aereo theme.
It works fine for the windows as they have transparent borders when not maximised.
But my taskbar is NEVER transparent, no matter if I have any window maximised or not.
I tried to go in the taskbar proprieties, in the Personalize panel but I can't get the transparency to work.
I would appriciate anyone's help,
Thanks in advance.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic