I would love a keyboard shortcut to the purple label. I use the purple label a lot and it would be really helpful to have a keyboard shortcut. CS3 appeared to have this functionality, but Bridge quit every time I tried to use it. CS4 does not offer the option to program a shortcut to the fifth/purple label.
Also -- if I change the names of the labels from the pre-programmed ones (Select, Second, etc) -- I lose all the labels on any items I have already labeled... they all go white. Apparently this is a known problem... it would be great if this was fixed.