Another trick is to edge your factions close to leveling up then leaving it there. Day one its easy to then go back, level them up, and get a package with a new TK weapon or armor. Least that is how it worked before, unless they are resetting faction levels also...
you will only be able to change factions once per week, although it sounds like you rep up both vanguard/crucible AND one of the other factions at the same time, so you can at least double dip that part. so yeah its still worth edging all the factions but you will only be able to turnover 3 max the first week - vanguard, crucible, and one more.
also they are crunching marks down to account wide, but i guess existing vanguard and crucible marks will convert to something else that gives you something? didn't really catch that part of the stream very well.
all in all sounds like it is gonna basically be a full gear reset but at least if you are 34 now you'll start at 34 instead of 20 on the way to 40, and then you'll have to grind out a bunch of stuff to get new gear so you can be good enough to raid normal mode. and of course you'll have to complete a shit load of new story quests and bounties to unlock the new sub class and start grinding the new faction reps.
i wonder what stuff like motes of light, strange coins, or planetary mats will let you buy on day zero. i assume xur will still visit to sell some stuff, but it also sounds like stuff like the gun vendors new weapons will be sold every wed like xur but you need to faction rep up, and the cryptarch will sell new legendary engrams for marks. Definitely interesting that theres no weekly cap on marks either, you can grind out 120, buy something, grind out another 120, rinse and repeat. do it all with a mix of PVE and PVP, whatever you want.
Its gonna be a bit scary in the first 24 hours of how much shit some people grind out, I bet we see full normal mode raid cleared within 10 hours.