The ease of use, speed to pay out/in money as well as being able to transfer funds between accounts is great! I have not experienced any problems with this service so far but it's always good to be prepared for something that could go wrong (which you never can predict).
If all goes smoothly there shouldnt really anything negative about using PD services at least in my opinion. As mentioned above nothing has gone completely awry yet; however if your looking into online banking solutions then maybe look elsewhere until they get their act together because currently i think its pretty bad compared what other providers offer when we are talking bank transfers etc..