1. Marth can be grabbed out of dash (in Melee too)
2. Tippers are exactly the same as they are in Melee. The visual swipe for the animation is different, showing the tipper range as more white as you move further to the tip of Marth's sword. A helpful indicator.
3. Yes! The pivot grabbing system works just like Brawl's (as far as I can tell since it's much more difficult in Melee). Although I don't think that a pivot grab after an l-caneled fair is guaranteed.
4. ^The gilde toss as LordShade said. Also the pivot grab mechanic. Only the things that the brawl system has allowed. Nothing was brought back from brawl Marth except his taunts.
5. Up throws for u-tilt juggles/u-airs. Chain throws (which you have on many MANY characters). F-throw to f-smash (which works on almost everyone in the game right now as far as i've tested). Retreating fairs, d-tilt approaches, etc. There are full threads on this.
6. Ken Fair Combo? Yes...?
7. It depends on who you are playing, how you play, and what character you're facing.
8. Shiek is actually easier now since she can't just fair you after a grab if you DI correctly in PM. Link is a tough one since his range is now closer to Marths and he has many more tools and options now. MK, if you end up below him but the MU isn't too bad. Mewtwo is easyish to hit but very hard to kill and he can approach you with teleports etc. ZELDA if you don't know when to shield. DIDDY KONG. If you don't have a good item game, you will get destroyed. Basically any character with a great recovery and ranged tools to keep you out and rack up dmg. LUCAS as well, since he can get in and wreck. I highly suggest picking up a secondary for your bad MUs.