I like these changes in general. Especially the Eladrin, for whom this opens up many of the "mind-bending" Int/Cha options that fit well for them. It also supports the Int/Cha shaper psion build in Psionic Power, which fits eladrin well fluff-wise, b/c of the new-agey/reality-bending feel to many of the powers, which fit an intellectual race from another plane of existence.
The Dex/Con build for halflings doesn't match that many classes, but it does help support the kind of psychotic halfling character (e.g. Belkar) who shows up a lot in my experience. Nice to have a less happy-go-lucky option.
The Str/Con options for dwarves makes an extremely powerful race more powerful at what it is good at. I like, b/c it isn't too powerful (no more than Shardmind for mental stuff) and the flavor is good. I would've liked to see support for Dwarven Artificers and Wizards, but Int just doesn't seem right...
I'm least happy with the change to elves. I like making them good swordmages, but otherwise, I think most Int-based arcane options just make more sense with eladrin than elves. The 4e elf is more like the wood elf than the high elf from earlier editions, and I liked the current emphasis on primal, martial, and striking. I think Dex/Cha would've been a better option, because it supports the more intuitive arcane classes (warlock, sorcerer, bard). It also would've made Shelly Mazzanoble's 3.5 elven sorcerer pretty optimal, which I think is a good kind of iconic build for the more... sensitive of new players. (Not meant as a dig, there just happen to be a lot of players out there who fit chick-lit RPG options like Blue Rose).