Hi,

I can only answer for Nxt, as it's the system I am most familiar with.

- I am not a huge believer in "first mover advantage". It also means you get most of the flack, because chances are you are also the first mover on problems.
- Yes, to forge, you need to have your account (brainwallet) unlocked
- I'm interested in this, too. I'm an old-timer in Nxt, so probably have a lot of blind spots here that should be much more obvious to newcomers.
- I commissioned this chart a few weeks ago, and it's at least checked by the Bitshares community, too. Other communities are welcome to critique, but it seems mostly accurate: http://i.cubeupload.com/J02n9J.jpg

As to the "value proposition": one of the large advantages of Nxt is that it supports a host of transaction types (standard coin transactions, data transfer, "alias" transactions, colored coins etc) that can be used in combination with each other to create entire systems. Taken by themselves they are useful, but the true power lies in being able to use them by easy API calls, so they can be integrated into websites, 3rd party apps etc.

What also appeals to me is that it is not dependent on a 3rd party blockchain, but is self-contained.