Not to throw a spanner in the works, but I just wanted to expand a little on the idea of 400 hours as mentioned by the devs. During my quest to uncover the secrets of the perk chart, I have uncovered a great deal of information that suggests highly expanded gameplay. For example, one area that has barely been discussed is the aspect of underwater exploration. As you will see once I post my full update, the actual origins of our protagonist couple means that they are both trained in underwater survival, and so this will feature heavily in gameplay. What I have found essentially proves that the husband is a Navy SEAL, and the wife is a Marine. By the very definition of Navy SEALs, this means that whoever we choose to play as, we will be extensively exploring SEa, Air, and Land, as has already been hinted at in both footage and concept art. Again, this will all make sense once I post the full update.
What this means in relation to the 400 hours is that the map for Fallout 4 is going to be HUGE. If we look at https://www.google.co.uk/maps/place/US+Army+Garrison+-+Fort+Devens/@42.5371685,-71.6175924,38312m/data=http://forums.bethsoft.com/topic/1530622-completed-perk-chart-speculation/!3m1!1e3!4m2!3m1!1s0x89e3eb75d050e27b:0xaa3ce0930ece76b4 image of Fort Devens, as well as https://www.google.co.uk/maps/place/Boston+Harbor,+Boston,+MA,+USA/@42.3387162,-70.975523,38434m/data=!3m1!1e3!4m2!3m1!1s0x89e36561b7075467:0x54d350088341b9e7 one of Boston Harbor, we can see that the two map markers are over 40 miles apart, and this does not even take into account the extended area around the harbor. I have uncovered very strong evidence to suggest that both of these locations will be included on the final map, and will be fully explorable. This means that the sheer number and diversity of locations in between will be unlike anything we have seen in previous games. It also means that the main quest, which will include full-scale dynamic warfare, will be playable over a very long duration. There will of course be those who will rush through and complete the game in 'record time', but I have a feeling that even this will take a great deal longer than previous games. To play through the game properly, including all side quests and miscellaneous quests, as well as the main quest itself, will likely take the full 400 hours quoted.
Finally, I just wanted to mention that I have added a small update into the OP tidying up a few of the descriptions, as well as explaining some new information. One thing I have discovered is that there are actually five different types of perk, each with different features and benefits. Also, every perk that has more than one rank (which includes 66 out of the 77 perks on the chart) also has at least one unique bonus feature, which is usually available at the highest rank, and will give us an incentive to take further ranks and not just the first one or two. One example of these bonus features is the additional information seen in V.A.T.S. during the E3 demo, as shown https://youtu.be/D5esyZPt5Jo?t=29m39s.
The rest of the perk descriptions should be up within the next few days, either in batches or in one hit if I can get them finished in time