I recently had the experience of parking up only to find the PODs were inactive, and as others have experienced, I had to wait ages for a bus which was not big enough to take everyone queueing, and so missed the first one. Luckily on my return the PODs were working otherwise I would have faced the note sending me down to the bus stop, so I appreciate it could have been worse.
The whole thing actually made me quite angry, not because the PODs weren't working (these things happen after all) but rather the substandard backup bus service, and that HAL effectively charged me for something they didn't provide. I expect all of this is covered somewhere in their small print, but it did prompt me to complain to HAL on the basis of poor service, which I rarely do. I filled in the complaint form and got a response within an hour with an offer of a partial refund. I felt it was fair based on the degraded service. In reality it was only a token amount which set me inline with the regular long stay parking charge on that date instead, but that's all I actually asked for. It was the principle of the whole thing that prompted me to complain. I hope others have had, or may have similar success.
The disappointment I still have though is that I probably won't book the PODs for the time being as I really don't want that feeling of "will they be working, or won't they". At least with the regular long stay it is consistent.