Really depends on your team-configuration, team-partners, your abilities to use mentioned champions, and as well as which play-style goes against which play-style.
I will tell you about my own personal-experiences with using Kennen. I like to use Kennen, a lot, but I need to use him when at least one other team-member is tank-ish enough or the other team-partners have synergistic crowd-control abilities. Kennen will nearly always be out-laned early on by those who can drop a puddle (i.e.: Morgana/Cassiopeia/etc.) & play solely for the purpose of pushing since nearly all Kennens will always start with his Q (and Kennen can only hit one target at a time with Q) and those puddles happen to hit/damage everything that's on top.
When I see a strong configuration on the other team, especially if they have the heal spell packed, I just tell my team to not bother with the pre-minion fight-scuffle since it would be to our disadvantage & just to stay back & focus on farming the minions for the time being instead (and this is a wise judgement in most cases unless I can see that our summoner-spells/team-configuration has a greater advantage then of course I'm all for landing that first-blood pre-minion scuffle to our early start-advantage).
P.S.: I got Kennen when he was 6300IP but I hear it's been reduced to 4800IP...