some thoughts on the summoner. ( and im biased, right off i love em )
first: SM spells have a tendency to loose there combat effectiveness at the higher levels ( they do remain the most utilitarian ones however ).
second: at mid levels ( 7th + ) a druid will be about 6 summons a day ( the highest level SM available at the level in question )behind the summoner, with all the other spells the druid has available to them i don't believe this makes the summoner OP.
third: i do not see why the summoner has a d8 HD and a 3/4 BAB. this seems a little out of concept even though there not "full" casters.
fourth: as for the eidolon. i love the idea, but there are people out there ( as we can see from these forums ) that will build them for pure power and not care what they look like or how they fit into the game, or even the theme of their characters. i hate to say it, but for this reason they should probably be changed.
i haven't run for one yet, and mine is only 3rd level, so i will reserve judgment on them for now. they are however the first "true" pet class we have seen, as i think there freaken cool : )