Okay, tonight I ran a Summoner and a couple of assistants against my 2nd level party. This is using the most recent updates.
My party consisted of (tonight):
Caleth, 2nd level tiefling B&E Rogue
Fairheart, 2nd level half-orc Paladin (AC spec)
Farin, 2nd level half-elf Ranger (Archery Focus, Uses Bastard Sword)
Alex, 2nd level half-elf Druid (Two-Weapon Fighting)
Wood, 2nd level human Fighter (Tank)
The party was up against 4 human skeletons and the following Summoner and his pet.
Alignment: Chaotic Evil
Gender: Male
Class & Level: Summoner 5
Race: Human (Skeletal Champion)
Init: +7
Speed: 30 ft.
Str: 12
Dex: 16
Con: -
Int: 12
Wis: 8
Cha: 18
HP: 57 (5d8+20)
AC: 20 (+3 Dexterity, +2 Natural, +5 Armor)
Touch: 13
Flat-Footed: 17
Fort: +5 (+1 Base, +4 Charisma)
Ref: +4 (+1 Base, +3 Dexterity)
Will: +3 (+4 Base, -1 Wisdom)
BA: +3
CMB: +4
CMD: 17
Attacks:
MW Bastard Sword +5 (1d10+1/19-20)
MW Light Crossbow +7 (1d8/19-20)
Skills:
Handle Animal (5 Ranks, +3 Class, +4 Charisma) +12
Knowledge(The Planes) (5 Ranks, +3 Class, +1 Intelligence) +9
Perception (5 Ranks, -1 Wisdom) +4
Spellcraft (5 Ranks, +1 Intelligence) +6
Languages:
Thassilonian
Abyssal
Feats:
Improved Initiative
Exotic Weapon Proficiency(Bastard Sword)
Arcane Strike
Spell Focus(Conjuration)
Augmented Summoning
Special Abilities:
DR 5/bludgeoning
Channel Resistance +4
Immunity to Cold
Darkvision 60ft
Undead Immunities
Skilled
Cantrips
Eidolon (Bloodleecher)
Life Link
Summon Monster III 7/day
Bond Senses 5 rounds/day
Shield Ally
Spells: (CL 5th)
1st- 5/day
2nd- 3/day
Spells Known: 6 4 3
0- Acid Splash, Detect Magic, Light, Mage Hand, Mending, Open/Close
1- Alarm, Magic Fang, Protection from Good, Shield
2- Bull's Strength, Haste, Invisibility
Equipment:
+1 Mithril Shirt
MW Bastard Sword
MW Light Crossbow
Spell Component Pouch
20 Bolts
Signet Ring
Ruby and Gold Circlet (450 gp)
4x Potion of Inflict Light Wounds
22 gp
Alignment: Chaotic-Evil
Gender: Male
Height & Weight: 4'2" & 240 lbs. (6' long)
Hair Color: Black with Glowing Red Runes
Eye Color: Molten Red
HD: 5
Race: Eidolon (Outsider)
Type: Quadruped
Size: Medium
Init: +3
Speed: 40 ft.
Str: 16
Dex: 16
Con: 14
Int: 7
Wis: 10
Cha: 11
HP: 47 (5d10+10)
AC: 19 (+3 Dex, +6 Natural)
Touch: 13
Flat-Footed: 16
Fort: +5 (+4 Base, +2 Con)
Ref: +5 (+4 Base, +3 Dex)
Will: +1 (+1 Base, +0 Wis)
BA: +5
CMB: +8
CMD: 21 (23 vs. Trip)
Attacks:
Bite +8 (2d6+4+1d6 Fire)
4 Claws +4 (1d6+1+1d6 Fire)
Skills:
Acrobatics (5 Ranks, Class +3, Dex +3) +11
Climb (5 Ranks, Class +3, Str +3) +11
Perception (5 Ranks, Class +3, Wis +0) +8
Stealth (5 Ranks, Class +3, Dex +3) +11
Languages:
Thassilonian
Abyssal
Feats:
Power Attack
Weapon Focus(Claw)
Improved Natural Attack(Bite)
Special Abilities:
Darkvision 60 ft.
Link
Share Spells
Evasion
Resist Fire 10
Evolutions: (Cost) 8 Total
Bite (Free)
2 Limbs (Legs, Free)
Claws (2)
Improved Damage (Bite, Claws, 2)
Energy Attack Fire (2)
Pounce (1)
Resistance (Fire, 1)
The party went through much of an ancient Thasilonian structure in the Lurkwood of Varisia, made by myself. Dverast was emplaced ages ago to protect the lowest level from intruders, and has grown mostly mad over the years. The party disabled a trap on the door to his room, which due to his charge, he could not leave without collapsing into a heap of dust. The party initially only saw the skeletons, blocking most of the 30' x 40' room, as they had set off his alarm on the door, and gave him time to prepare. Due to Protection From Good, Shield, and Haste, the party was severely outmatched and was nearly wiped out when Dverast summoned a pair of leopards, as at that time the fighter was missing. They managed to destroy the skeletons and take Bloodleecher to half life before retreating. They took a two day break before challenging the room again.
When they challenged the room again, they were bottlenecked by Bloodleecher in the entryway, but as they had triggered the alarm and run before entering, most of Dverast's spells were expended. He joined Bloodleecher in melee after casting Bull's Strength on both of them, trying to take down Fairheart the Paladin. Fairheart had a 23 AC vs. Dverast, and 27 vs. Bloodleecher due to Smite Evil, which made it a drawn out battle. Fortunately for Bloodleecher, he lacked the Evil Subtype, which kept him from being destroyed. The summons that Dverast tried this time were rolled over after dealing perhaps 5 damage apiece, but the party was forced to retreat after Fairheart and Wood were knocked unconscious, and Dverast couldn't pursue. As Bloodleecher was at 2 hp remaining, and Dverast was without any additional way to heal, they decided to cut their losses and wait.
My conclusions: The Eidolon is very impressive, especially when buffed and if you can get support. The summons are very situational, but it's far too easy for intelligent foes to make you waste them with the short duration, same with the spells. And it is not recommended to make an undead Summoner unless they have some way to heal themselves, as their Life Link is nearly useless.