Almost everything about d3 that they are pushing is more customization, more randomness, but the removing jewels for sockets and replacing them with just pure gems removes a lot of the randomness and a lot of the customization. I really liked the jewels in d2, you could have 4 random affixes spawn on rares, or two on a magical ( but the affixes were slightly higher) and it made for a lot more customization and added a lot of randomness of the drops (especially for the rares, was quite hard to find a good one but when you did they were amazing and extremely valuable)
But I don't know if its just me, but the gem system in d3 seems a little boring/generic. There were gems in d2 but they were never really used for socketing items, they were mostly for crafting and sometimes if you were a new player you would use them for sockets (there were some rare instances when gems were good for high level socketing but very rare instances like for druid pelts with perfect rubys). Having gems that just sort of have no randomness to them other than that they increase in power the higher the level of gem just doesn't feel diablo to me, it feels way more like a mmo version.
I'm hoping the future expansions bring back jewels because they really did add a lot more customization as far as gear goes and added a lot more randomness to the game. It makes me wonder why they decided to drop that system and put in a gem one, especially with all the other changes to the game adding a lot more customization as far as gear goes.