As far as Siddious was concerned, Geonosis went off without a hitch - hundreds of the Jedi's best and strongest dead in a day, a war that would distract and corrupt the Jedi started, and him the top level of control on both sides? Utterly perfect. (And cherry on top, his chosen apprentice Anakin Skywalker survived.)
As far as the Jedi were concerned, it's more complicated. Windu spent most of the book Shatterpoint worrying about whether or not he should've just killed Dooku on Geonosis and perhaps ended the Clone Wars before they started, but SPOILER SPOILER SPOILER ends up deciding that to have done so would've crossed too many lines, both in ethics and in the Force, that for the Jedi to embrace that sort of ends-justifying-means perspective would've doomed them on its own. Of course, he didn't know about Siddious or his plans, so he had no way of knowing just how much he did exactly what Siddious planned for him to do - that knowledge probably changed his perspective, which I suspect accounts for his changed position in the Revenge of the Sith novelization.
From my perspective? The Jedi did the wrong thing for all the right reasons, and had no way of knowing it at the time. They walked into a casino to play blackjack with the Republic and the Separatists, trying to keep an eye on things because they thought a Sith was wandering around the slot machines, and didn't realize until they'd lost all their money that the dealer was the Sith all along - and the house most certainly won.
Edit: Think of it this way - had it been, say, Poggle the Lesser and Nute Gunray on the podium rather than Fett and Dooku, had Gunray gotten the lightsaber under the chin... do you think Gunray would've chosen to fight at that point, to have droids start shooting at a target a meter away from him, to risk his own head being cut off regardless of whether the droids win in the end or not? No. The Separatist leaders were nearly all CEOs and politicians - Poggle the Lesser was probably about as military as they got, but I simply don't see him pulling a flamethrower on Windu. Without Sith being the ones in charge, without there being an ideological agenda behind the Separatists rather than simply a financially self-interested one, the Jedi "this party's over" entrance probably would have worked and ended things without blood or money spent (droids are expensive, yo, and those 200 Jedi did bust thousands of droids even before the clones showed up, who then busted tens of thousands more plus ships/armor/factories).