I have that bird bath and I use it as the water dish in hopes my budgies might use it as a bath. In the 18 months or so I have had it, it has been used 2 maybe 3 times as a bath. I was astounded each time! Once one budgie decides to have a bath, the other 2 become interested as well. It's so cute!
It's not as convenient to change the water as the water dish that came with the cage but I think it's worth it for the occasional bath.