It depends how lucky you are -- imean on which page you get listed. If you get PR7 backlinks like Aviva and Alive got--then yes it is worth spending $299/year as a noraml PR7 link cost $420/year ($35x12). About getting pagerank-- I am not sure. A mere Pr7 link is not going to make you PR5/6. For that losts of such links are required.
If you really want High Page Rank backlinks heres a TIP for YOU and there are NO supreme BS and just mouth talking. If you submit now.... You save more before PR Update since MOST Directories will increase their prices once they hit the slot they are aiming. It might be included in your BL. It can definitely give you quality links that a site needs. What are the SITES ? There are many you just have to look for THE REAL THING. How would I know if the site is the REAL THING ? Easy just go and look for their BL's and that will tell your answers.
just submit to free directories. They will stop being free once they have over PR4. Chances are that some of those will get PR6, and you will enjoy your free PR6 links.
Yeah the most is 5. Chances are when they get to 6 they gonna take off your links and you have to buy. Also as experienced as someone like you chances are the MODS at DP can get to your account and investigate for duplicates. Good Luck.