Let's get these pineapples to Hawaii before the price drops!
Probably every DM has used the "caravan guard" adventure hook at one point or another, and merchants themselves are not exactly the scariest of monsters unless you are particularly susceptible to extended warranty sales pitches. But the more I look at the Cook Expert listing, the more intrigued I am.
Like bandits, merchants are not so much a memorable encounter by themselves, as what -ahem- baggage comes with them.
The no. appearing is listed as 1-20. What's fun is the chart on X36. Depending upon how many actual merchants there are, the caravan just keeps growing. An average roll of 10-11 merchants means twenty wagons. That means at least 20 teamsters plus draft animals (mules, etc.); probably 2 per wagon. THEN there are the extra 1d12 animals.
The merchants themselves wear chain and carry swords, so ten or so of them are relatively formidable. However, the really interesting thing are their guards.
For the 10-11 merchants, that's 45 fighters in tow.
What's more, that includes four 2nd-3rd level fighters plus a FIFTH level guard leader.
I'm thinking these guys aren't going to be terribly easy to intimidate. Nevertheless, twenty wagons of goods and supplies plus forty or fifty riding/draft animals must be a tempting target for some. (Not to mention the weapons and armor from the guards, etc.)
Another aspect of the merchant encounter that is worth noting is how useful they are at handing out rumors and hooks. Merchants generally talk to everyone from all over and keep their eyes and ears open. Smart players will make nice with merchants, and pump them for every scrap of information they can.