Runes in D2 are little things that you use to socket and enchant equipments, and specific rune combinations would also create runewords.

Now runes are coming back, but in a different way. Instead of socketing item, you'll be socketing your skill, enhance the skill depending on the quality and property of the rune.

It is said that all active skills would have a socket for runes.

It sounds really interesting for me. Back in D2 before the synergies, there are only several builds that are "good." (A lot of builds are fun, but not "good" in terms of PvM or PvP) So, when you look around, you will see a lot of players to be almost identical to you in terms of both skills and equipment. WW baba, Javazon, Bowazon, Zealot, Orb/TS sorc, you name it. (There are some changes after the synergies were added, but not enough to really change things)

But with runes being able to modify/customize the usage of skills..

I'm just really looking forward to the whole game right now. Also, they could expand the gameplay simply by adding new runes in the future.

I am a little worried about the rarity of the rune though. I hope the top level runes will not be as rare as Ber/Jah/Zod..