it doesn't help for summoning creatures, no, unless you're casting a spell that requires the summoned creature to save against you (I think gate? Probably planar binding too, my summoner isn't a high level yet), in which case it adds to the DC the summon needs to beat to resist you.
Don't forget the non-summoning spells that it likely boosts, especially if you're a conjuration-specialist wizard: lots of acid spells and some force spells. Just because the iconic acid spell - Acid Arrow - doesn't allow a save, doesn't mean all the other "no SR take acid damage" spells don't allow saves - and SF:Conj makes them that much tougher.
(And then, Augment Summoning is so broken that it deserves to have more prereqs anyway - you know the little Viper you can summon with Summon Monster I? You know its poison save DC is Con-based, right? So Augment Summoning adds two to that DC. Also, see if you can get your DM to let you repick feats for your summons, especially getting rid of worthless feats like Improved Initiative (since the summon doesn't get to roll its own initiative) and take things like Ability Focus: Poison (ANOTHER +2 to that DC!). Last night my summoner picked up a Lesser Metamagic Rod of Maximize Spell and tossed a Summon Monster III through it for 1d4+1-maximized-to-5 Vipers with boosted hp, fort saves, chance to hit, bite damage, and a 17 save DC on that Con poison.)
