We've had then since the station makeover. Never used them, just cos I haven't needed to park there for years.
Having had a bike nicked from the old station, I'm inclined to think your bike is much safer* on the upper deck than in "normal" parking. But perhaps I don't think like a bike thief - do we have any here to comment??
(Note "MUCH SAFER" - which does not mean IMMUNE TO THEFT ! )