@Wayne ********
I've never had issues with either - only once was I stopped at customs (technically it was my wife) but only due to an unusually large amount of luggage that we were carrying, well above the normal check-in limits (though with my frequent flyer status and being a personal friend of the check-in agent at the origin, it was fine).
Immigration I've not had an issue with either, but the OP might, hence the question. People are paying for VIP status for one of two reasons (or sometimes both):
1) to save time on entry into the country. Having to stand in a queue, possibly for up to 45 mins in close proximity to hundreds of strangers can be both nerve wracking and claustrophobia inducing. Those who aren't good on their feet might struggle.
2) because they have a not so stellar immigration history and the VIP pass ensures they'll be able to pass through immigration without incident.