Mark Chance
Boingy! Boingy!
Have you looked at the Pathfinder Summon Monster lists? Many creatures come in a full level earlier than they did in 3.5. It's a significant change.
Interesting. I hadn't noticed that.
I did, however, notice this generalization:
Summoned monsters are generally of a CR significantly below the party level, fighting against monsters equal to or higher CR than the party....
That's not true in my games. PCs in my games generally fight against groups of monsters with individual CRs lower than that of than the party. For example, five CR 1/2 monsters (EL 3) against four 3rd-level PCs.