One of my two most commonly-run characters is a Halfling Master Summoner who - for RP purposes - only summons Elementals. We've made a Small and Medium Elemental of each type to fill out the Monster Summoning I and III lists and have also created several other elementals as well (Stone, Crystalline, Smoke, Steam, Acid, Dust, etc.)... in the process I've had a chance to really examine Augment Summoning and my GM and I have come up with what we think is a 'better' version of it.
First off, the benefit scales with level, granting +1 to Strength and Constitution at 1st, +2 at 4th, +3 at 8th, +4 at 12th, +5 at 16th and +6 at 20th. Its a little less powerful for most of the character's life, but better reflects the relative power of ever-increasingly potent summons.
Secondly, to make up a little bit for the early diminishment of power, the bonuses apply to Dex and Con instead of Strength and Con IF the creature has the feat Weapon Finesse - its simply inappropriate to boost the Strength of some Dexterity-based creatures.