I say almost perfect because there was one tiny flaw in their planning: they forgot to account for one of the baddies's familiar, a bat. Their own standard procedure when traveling is to send the familiars ahead to scope out trouble or whatever -- it didn't occur to them that the badguys (who were 7th-9th and experienced adventurers as well) would do the same. I got Hide checks from the whole party vs. the bat's Spot check, then gave the PCs who would have a chance to notice the bat Spot vs. its Hide ... and they missed it entirely.
Thus, the baddies came into the ambush knowing the PCs were there. On the good side, the baddies didn't know that the people lying in wait for them ahead were a powerful party -- they assumed it was a handful of scruffy bandits that they'd just take out quickly. Overconfident, they went into battle unbuffed, rather than buffing up first and then coming around the blind corner -- that would have been a much tougher fight!
The first several rounds were an exercise in frustration on both sides; the baddies stood around casting buffs but were unable to achieve much due to camstone's well-placed entangle. The PCs, on the other hand, kept rolling badly and were pretty much unable to hurt the baddies. jamesbarrett's wizard Kyriela, in particular, spent the first several rounds contemplating her navel due to an enemy bard's fascinate.
Things started to look bad for the heroes as the badguys launched into their more damaging spells ... confusion and glitterdust being particularly worrisome. But then Ulf used countersong to break the fascinate and Kyriela hit the field with a dispel magic -- almost all the baddies' buffs went byebye, leaving them almost out of spells and facing a mostly-fresh party. Jaer went into "pincushion" mode, Dragor fired up the whirling dwarven waraxes of death, and Verdhaven and laurie_robey's rogue/fighter Angelina showed why "grapple" is considered the single most effective way to take out enemy spellcasters. A few short, violent rounds later, "The King's Players" were a dim and unpleasant memory.
Usually the party is in reactive mode -- chase the baddies who have a prisoner, or get ambushed and fend them off, etc.; so for them to carefully and methodically study the enemy and take 'em out like this (including spying on them the night before in a tavern) represents a real step forward in their adventuring "technique." It was also a learning experience -- "Oh, dang! They have familiars too! We'll have to plan for that in the future..." Even that slip wasn't a plankiller; it just meant that there was no "surprise round."
So, well-played, guys! :) Now I can beef up the opposition a bit more for next time... ;)