So X/Y is worth it? Should I forget about my B&W2 progress and trade up?
I love it and do suggest getting it. There's something about seeing your pokemon in full 3d modelling that changes the entire game for me. I have actually been working on B/W 2 in order to get the legendaries and end game pokemon on it to my Pokemon X game.
But, that said, I'll do a quick unbiased review of it.
It's the basic Pokemon story. I won't give any spoilers, but you've really seen it before. Pokemon are your best friends and you can save everyone with them. There's also not as much end-game content as there was in the others. There's a decent amount, but end-game is seeming like it's pushing more towards doing online battling and trading. There's the megastone hunt, the legendaries to catch, and a battle institute at the final city to go through and master (which is actually pretty difficult since the institute uses player battle rules. No items or switching between pokemon after a knock out.) But as far as the online battling goes, it's probably the most in-depth it's ever been. Super training is great and it really extends the game. Pokemon-amie also plays a part in battling. The happier your pokemon is, the higher it's crit and dodge ratio.
It won't get to constant crit/avoidance levels, but it makes a difference.
But, that's really it for the downsides. It has a good blend of classic and newer pokemon and they did away with the classic grindfest with the new Exp Share, which I both like and dislike. It made all the gyms and elite 4 just a bit too easy for me, but it means you can juggle entire extra teams of pokemon while you're going through the story. I had about 18 pokemon up to level 70 by the time I finished the story-line. All starters included. One thing I like about B/W 2, despite not really liking the both of them, was that you felt underleveled the entire way through. That's not the case with this one, and that can be good or bad depending on what you're playing for. Makes it easy to get to end game online play, but it cuts out some of the potential content.
On the topic of starters, it's really easy to collect all of them. I traded for them on GTS for some haunters/gravelers. People who are stat prioritizing through breeding will use the duds to trade for harder to find pokemon, or the ones they're too lazy to go out and catch so the evolve-on-trade pokemon are gold right now. I got about 50% of my pokedex through just trading haunters.
So, in summary, it is a great game and will consume your soul. I'd totally recommend it. It's a much needed technological step and refreshes the entire series for me. Also, go watch Pokemon Origins.