Another thing to consider about the Summoning ability is that as a SN ability it is cast as a Standard Action unless otherwise noted, per the rules listed for the Binder's SN abilities in the class section. This is a huge advantage over traditional summoners as it allows for more actions and prevents interuptions, though again SN abilities generally can't be interupted.
I know in my current game my DM decided that it would be 1 monster at a time with a Full round action to cast and I'm still the most powerful and versatile PC in the group.
If I could go PRC classes that improve caster level as well as binding I would definately go with an anima mage type build, and Gish like crazy. Add in either 5 levels of KotSS or Zceryll to become an outsider and anything that grants Alter shape or Polymorph for the NA bonuses alone would be awesome because you could pick from outsiders = your HD. Dwarf Ancestor gets an insane NA bonus, something like +16 NA though I don't know what it is exactly. Add on your normal gish abilities and if you bind something that grants turn attempts or smites use them to fuel Devotion feats for extra unlimited goodness.
- Tenebrous with Travel Devotion, is 1 move action as a swift every round plus a full attack action. All day.
- Shield of Mercy with Andras is unlimited healing as you turn your smite damage into lay on hands effectively
