ZSutherland said:1. Do you feel the Summon Monster series is strong or weak? Why and to what extent?
I would agree that they are pretty balanced. Summon Nature's Ally is better at low levels, but that's because SM creatures are considered to be better since they are celestial or fiendish. Once celestial/fiendish creatures reach 5HD (SMIII), they get DR, which makes them more attractive. Even lower level SM creatures get smite good/evil. I've only experienced these at lower levels, but I'm considering taking them at higher levels for my sorcerer.
ZSutherland said:2. If you use these spells, or your players do, what are their results? How are they commonly used. If you don't use these spells, why not?
Flanking has been mentioned. You can also put them in a position to make AoO. Choosing flying or fast creatures makes it easier to pursue.
The most impressive use of the spells was in an encounter where everyone in the party had been incapacitated (by a yellow musk creeper), except the gnome cleric, who was being pursued (slowly) by a couple of zombies. She pulled out a couple of summon monster I and II scrolls (using the latter to summon multiple SMI creatures) and managed to kill everything off herself, saving the party.
ZSutherland said:3. Is it class specific? I.e. is it worth it for wizards because it's so versatile, but not as much for clerics since they're restricted by alignment. What about sorcerors?
Druids (Summon Nature's Ally in their case, of course) can summon spontaneously, which means they can really take advantage of the versatility. My third level druid has done this a number of times already. Likewise, sorcerers can spontaneously cast SM, if they take it.
A friend has a cleric1/wizard2 built as a summoner. He has the good domain, so he gets an extra round out of his SM spells, and he is a conjuration specialist. He usually prepares 3 SMI spells and no Magic Missile. It's not bad, but the fact that we go through his Magic Missile scrolls like they were going out of style illustrates that this is probably not an optimal build.
ZSutherland said:4. Are some iterations of the series worth more than others? I.e. is it worth a 5th level slot to summon a Hound Archon for 9+ rounds, but not a 4th level slot to summon a lantern archon for 7+ rounds?
It comes down to the value of the spell compared to others of the same level. SMI will look bad next to Magic Missile, Mage Armor, and Shield, among others. SMIII also has too many good arcane spells to compete with. SMIV and higher are interesting because celestial creatures have DR starting at SMIII, so you can summon a bunch of celestial lions with SMIV or SMV, not to mention other good things, like archons.
ZSutherland said:5. Whatever else you have to say on the topic.
Overall, I think they are good spells with good versatility. My 3rd level druid can now summon hippogriffs, black bears, crocodiles, and dire bats, which each come in handy in different situations.
--Axe