The replies are a bit mixed so far, so I'll chip in. I play Acquire with three people on occasion and there's absolutely nothing wrong with it. Acquire is one of the few games where I can honestly say that nothing is lost when you go from four to three players.
I haven't played that many games of Acquire, but we like it in general. I haven't noticed it being poor with three players compared to four.
I may be depricating the value of my response by adding... we've mostly played it with just two. There's some fairly obvious competitive and strategical elements lost when playing with just two but it's still a good game. (With or without the random market owner.)
Acquire is playable with 3. There is a lot of tension in the early game. There are times when the third player can be blown out of the water in the mid-game, but this can certainly happen in games with 4+ players.
That being said Acquire is still a fabulous game for 3+. I find it lacking for 2-player (the banker mechanic works, but it occasionally creates blow outs), but I do, on occasion play it as a 2-player game just to get a fix.