Weapon weight absolutely crippled low constitution and low strength characters like Monks and Myrmidons, and made their power even more luck based than it already was. Basically, if you didn't get a strength boost (even though Mages wouldn't use Strength and thus had very low growth), you couldn't use any of the more powerful weapons. I am not sad to see it go.
Pair up is a fantastic idea with questionable execution, admittedly. I still vastly prefer it to Rescue, and, while there is still a ton of balancing to be done, Lunatic and Lunatic+ show that the game can still be easily built to counter the bonuses it gives you. Again, they didn't do a fantastic job of that, but given how many new features they had to try to balance in Awakening, I thought the result was really solid.
I do miss Fog of War and destructible terrain, though.