I think that the classes hit die and BAB should be scaled down to match that or the wizard/sorcerer. Having said that, I think the rest is fine. I like the increased duration of summon monster spells; one of the largest complaints I have with the duration is that it leaves little time to do anything else with it. A summoner lives and dies by his summon monster spells; his spell list is extremely limited, more so than a sorcerer. He has less options, being restricted to 6th level spells, and possesses a smaller number of spell slots in which to cast the few he does know. The summon monster spell offers greatly needed versatility; it has to last longer than the standard few rounds for the class to function outside of battle. Otherwise, the summoner would be nothing more than a supremely limited spontaneous caster.
As for the problem of the summoner spamming his abilities and hogging all the glory, I doubt it would be much of an issue. Seriously, I don't believe that the summoner has the resources to blow all of his summon monsters at once, not unless its a major battle, and even then it's a non-issue; summon monster was nerfed like most other spells in Pathfinder, and frankly, most most of the summons will pop in the face of a moderate threat.
I'm fine with the eidolon. I wish animal companions were more customizable and versatile. I hope people give the class, and the Witch as well, an honest go before trying to beat it to death with the nerf bat. I know I will.