Sadly you will be gimped because some items are exclusive to high levels of light or dark alignment, such as relics and some armor pieces once you hit the 40s. Relics is a big thing to use but not necessary, just means you won't be able to have burst damage/healing.protection so you can be outperformed by other players.

This is a great system which was implemented in wow to lessen the frequency of ninja-ing gear on their servers. I know people on the forums here will dislike the idea because it one of two reasons. One they are ninjas (in swtor's case: jawas) and want to make money by stealing crap from people who are going to use it. Or they may just be the avid anti wow player where they dismiss that any system or theme ever used in wow (whether or not it was implemented in other games) is automatically considered a bad idea to them. In summary TOR needs this system, it will help deal with cross class ninjas but I don't see popular vote giving the system it's time.

Most of us with early access probably will have to wait until launch day (no matter what date you bought the product)

They are made to be done in a group difficulty but not to be confused with flashpoints.