The only parking app that I had experience using was SpotHero. The process for entering and exiting off-street parking using the app was fairly simple. Being able to reserve a parking spot in advance also removed the uncertainty of having to search for a space that was not already full.
Unfortunately, I found that the daily rates were rather high in proportion to the monthly rates. The daily rates were typically between 7% and 15% of the monthly rate for the same locations. This would mean that on average, a weekday commuter would need to shift to a modal split of at least 50-50 just to break even on parking expenses when compared with the monthly rate.
In addition to the higher proportional costs, I found that many of these parking locations would also not include in/out privileges at the daily rate. This would have prevented me from leaving work during the middle of the day to go to an appointment without paying for parking a second time.
Although I was willing to accept these limitations, I would imagine that many other commuters would not be interested in accepting these restrictions.