I'm in need of a full motion mount for a 40" tv and was curious about the mounts that Monoprice sells. I seem to remember people liked them, but their low prices give me pause. Are they good to go or should I be looking somewhere else?

I've never bought anything from them that wasn't excellent quality and exactly as described.  I'd buy a mount with confidence.

I agree with this

I've bought a couple from Monoprice. Quality is better than I expected as well, stick within the limits and you'll be fine.

I have used a couple of them and had no issues.

The thing is, most of these mounts are made in the same place, and are identical, except for price. Years ago, like in 2006, I bought my first LCD TV and was looking for a mount. At a now closed up place, I saw a mount for $89.95 with a supposed list price of $99.95. I went over to Big Lots, and they had a suspiciously identical looking mount, in an identical box, except the colors were reversed, with a different name on it. I bought the Big Lots one for $20, and a friend, who didn't ask me about it, bought the one for $89.95. And they were the same mount. They even had the same bizarrely translated instruction "manaul", as it said on both of them. I've seen a half dozen of the same exact mounts since then, sold under a bunch of different names, for all kinds of different prices. Since then, I haven't spent more than $20 on a mount.

They are good to go. I've used them for all my tv's over the last 5 years.