Runes, imo, mainly hit jungle the hardest. Try jungling without a book and see just how much more roughed up you get in there. although mainly when you're pre-30 where you only have like 2 armor from runes.
As for level 30's, a full set of T1 runes should put you close enough to T3 runes so that it's mainly a skill difference, the better runes is mainly a tie-breaker for very closely skilled players. If you know you're fighitng players who have more runes than you, just play more defensively, they still can't dive towers.
What I don't like are T2 runes. They're expensive, they lure players into getting them over T1 runes, and you will have to replace them with T3 anyways, not only that, they're barely an improvement over T1's. That is the true noob trap.