PAP = Premium Annual Pass. AP = the regular Annual Pass. DVC members get a discount on these passes if they want to purchase them. Since owning DVC makes going to Disney a lot easier, and often staying longer, the AP's make sense for a lot of people.
To answer your question, there are absolutely no hidden fees. Aside from the original purchase price and annual dues, there are no other fees to use your points at DVC resorts. No fees to bank or borrow, no fees to make reservations. No taxes to pay, thus no sales tax, no resort tax etc (regular WDW hotel rooms have an 11.5% to 12% tax applied).
You may also use your points at some places other than DVC resorts and have no fees. This includes most WDW hotels, DL hotels, or even Paris or Hong Kong and there are no fees at all if staying in these places. In fact if staying at Paris
Disneyland, you also get free park passes and free breakfast.
Now in other cases, there are fees you might want to know about, but all of these are optional items.
The smallest fee is it costs $0.35 per call to use your in room telephone for local calls. (Non-owners are charged $0.75)
Optionally you can purchase extra items to use during your stay, such as extra towels, soap, etc. Most users don't do this and simply use the washer/dryer to 'freshen' up their towels, and then get the regular clean set (free) on their 4th day. Some users however want fresh towels every day so they can get them if desired, for a fee.
Optionally you can pay to have your room cleaned daily rather than just have the standard Trash/Towel cleaning (or full cleaning, depending on your length of stay) which takes place on day 4, day 8, etc.
There are fees to use your points elsewhere such as for the Cruise Lines, or non-Disney hotels, Interval International exchanges, and such. In these cases these fees are generally in the $75 - $95 range, per reservation.
Finally, it's not a fee, but, if you didn't know, you may valet park for free at the DVC-resorts which have valet service (BWV, VWL, BCV), but it is still definitely appropriate to tip. Of course, all the resorts have self-park also, which is free.
Finally, keep in mind, that DVC resorts are considered no different than any of the WDW resorts and DVC-members staying there do receive all the regular 'perks' for WDW resort guests. This includes things such as free parking at the theme parks, Early Entry, etc.