I played Bid with three players and an extra pre-gen, and I wish we had played with more players. With just the three of us, it felt like we were just barely on the edge of failing, which helps with the dramatic suspense, but doesn't help in terms of "you must have this many PCs in order to win".
Also, I've never read the Ultimate Intrigue mechanics. I don't own the book as I wasn't entirely sure that I wanted to try to play Batman in Pathfinder. However, the scenario does a decent job of educating players as how it works (or maybe that was the quality GM we had).
I need to say that my GM did a fine job of using suspense to keep us on our toes, especially with revealing skill check results and which bidders were where in the status updates. There were a few times he had to double-check things, but I think that any GM is going to have to thoroughly prepare this scenario to make sure they understand everything. (I would hate to try to run this myself because of the complexity.)
That being said, I have to agree with another reviewer that the lone combat scenario didn't really add anything to the scenario. It felt very much like it was tacked on in case there were martial PCs in the group who were going to feel useless later on in the hobnobbing section. If the PCs have a chance of rescuing someone who might have a chance of influencing the action later on, the combat would feel less superfluous but as it is, it's very much throwing the martial PCs a bone, and that's really annoying.
(I did like the terrain that was used in the combat, though! It would be neat to see that terrain used again in a different scenario.)
Another big problem with the scenario is that it relies heavily on 1-2 skills that very few PCs put ranks in, or have as class skills. It's possible to use skills that you're more likely to have, but the scenario essentially punishes you by having higher DCs for those skills.
The NPCs were fleshed out well, though I find that with the social mechanics, I wanted a way to be able to "attack" the antagonist's efforts, either by disrupting their own schmoozing or whatever. I know it wasn't a combat or anything like that, but being able to see the antagonist also have to work in order to get their results would've been nice. (Maybe I've been playing too much Vampire: the Masquerade?)
The reason I gave it three stars is because of the following:
1. The combat had potential to affect the storyline, and even I could feel that it was there to placate specific types of PCs.
2. There was no way to "attack" the antagonist's efforts (at least, not that I could see).
3. Holy *#$&, there were a lot of handouts! With a scenario this complex, it makes sense, but when even the players are having to flip back and forth to figure out what to do to who for how many cookies, it seems a bit much?
4. This scenario forces players to play only social PCs. Social PCs getting the spotlight is wonderful, but if caster PCs or martial PCs had been able to bring their skills to bear to affect outcomes, it would've felt more like a scenario where even a fighter could assist.
5. It feels like you need to have X number of players at the table in order to adequately get all the information you need to in order to win, which can be a problem when there's low attendance or just not that many players in your area.
