If you would take a look at eg. the login screen of hotmail, you would see that the empty text doesn't disappear when the field receives the focus. I hacked myself a solution too, to provide this with the current textfield, but it would be nicer if maybe you guys would provide it out of the box?
I have even seen a better example that even changed the font color (of the empty text) a bit when the field received focus.
My current code, which still has some issues with the cursor when selecting: http://pastebin.com/KHqZH1Bz