The distortion is not always a negative. It's more of a problem if you are looking at it from an odd angle. And they arn't any harder to place then a normal tank. They tend to be considered a bit more decorative then the standard rectangle tank.
Now one negative is they can be hard to sell. Not because people won't buy them, but because most the time it seems the people who try to sell them think they are worth 10x what a normal tank is worth.
As for craigslist around here. An empty tank with equipment is cheap. A tank setup and running is a small fortune (even though it'll need to be broken down to move). People seem to think if it is running and established it adds a ton to the value. Especially saltwater setups.