Sorry, I didn't stick around the generals from when this show was still relevant, so I don't know what the general consensus is. I really just picked this up because I saw a webm where some middle aged ladies tell a fat businessman they're going to report them to the police, so I immediately thought "this is my type of show" and decided to watch Warau Salesman NEW some time. I haven't read the manga so I can't comment on that, but I'll lay out my general theory I think people need to understand to not think "wow this salesman guy is a total douchebag this show sucks he's CHEATING them"
I'm only just up to episode 7, but I've seriously been hooked on this show, I wish I'd had watched it all with you guys earlier but I prefer batch torrents. So the way I think of it is, deadly habits and mistakes a perfectly likeable person can make are personified as the "Smile Salesman" youkai. Of course, he's not ACTUALLY real, he's just the temptation to come up with a solution to your problem that doesn't actually solve anything in the long run, the temptation to not improve yourself, and just try to ignore the real issue. He always understands the person he's speaking with, and urges them to make a move, and he absolutely never tells the person he's selling to is wrong. He'll support them all the way to disaster- the Warau Salesman isn't an intruder, but just the stubbornness inside everyone.
Hence his appearance as a smiling con artist, selling miracle cures to any of your troubles.
As for my comparing him to a youkai, he doesn't do many things that are strictly impossible, but he just turns up in a person's life and ruins it, much like a youkai. It's totally unfair, and it could happen to anyone. One bad thing this does for his appearence though, is people ACTUALLY think he's some demon looking for a reason to screw with people (like Kuchisake-onna, or the Wolf from tale "The Wolf and The Lamb" from Aesop's fables (The moral of that story is: "The tyrant will always find a pretext for his tyranny")).
The second point is, this isn't a comedy show as most people expect jumping in (the appearance of the main character doesn't do that any help), it's a show where you watch good people do bad things, and you just want to yell at them to stop. It's "real horror", as I think people call it.
The reason I'm making this post is, I just saw the episode with pic related, and sucked. It was absolutely terrible, and I think it went against everything Warau Salesman is about.