[jQuery] serialize() doesn't collect <input type="submit"> value

I' was reading about the new jQuery 1.2 serialize() and I don't know
if
it's a bug or an intended feature but with $(":input").serialize() or
$
(":input").serialize() I can't get values of submit buttons?
The same goes for <button name="xyz" value="zyx">.
Is this the way it should be???
I always test against those elements to see if the form is submitted.
Greetz