In my experience, the effectiveness of Priority tags is also largely dependent on destination airport; In the past 12 months, I have noticed Priority tagged bags come off first at:

Singapore Changi
Kuala Lumpur
Cape Town

but not at:

Bonaire
Aruba
Hong Kong [they seemed to have this system of removing everyone's bags from the baggage reclaim belt and placing them in a pile there, 'Priority tagged' or not]

and certainly NOT at:

Manchester [in fact we are usually grateful our bags arrive at all when we get home to Manchester!! ]

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KLM FD PE, BMI Gold, AA Platinum, UA Premier, HHilton Silver