One thing Team Builder had that people may miss

The ability to pick your champion and role for certain before finding a team.

I'm on the other side of this, where my favorite part of TB was the fact I get a certain role, regardless of the champion. I love the new setup because it gives me exactly that, along with the ability to form a team with synergy instead of kicking every jungler because we needed a second knockup for Yasuo.

A friend of mine, though, was very upset that he can't use a for-sure role+champion mode any more.

Just to be clear I don't miss that aspect. I thought it was a hindrance to forming a viable composition anyway.

Side note: I do miss the ability to change my runes in the lobby. The fact that's no longer possible means some people are going to get stuck with my AS runes on Riven because Rune pages cost as much as a brand new champion.