Their design (make-up, latex face bits, outfits - especially in DS9) all looks great.
I liked them in "The Battle", and in early TNG they had some cool camera angles and vantage points in showing them in full view on the viewscreen...
As with most characters (good or evil or otherwise), most start out rough around the edges - too rough and they're not going to be necessarily remembered in a good light. Their first full story is so clunky, inanely sophomoric, and heavyhanded in approach that I needed a doubletake on who edited the original teleplay to work out the kinks. It didn't help that "Encounter at Farpoint"'s handling of how they're said to eat humanoids was not given any dramatic weight - never mind lack of showing it or hinting at it, spewing exposition did nothing... It didn't help even more that they ended up being fodder as comic relief in later TNG episodes. Even in the classic third season, save for "Menage a Troi" and specifically Ethan Philips for nailing his role incredibly well - the guy's got impressive acting range -- and it's nice to see a Ferengi come across as properly menacing. That's what was needed from the get-go. But I digress, here's a screencap from an early episode - early TNG had some great camerawork and lighting (barring the black cardboard panels put over consoles in some scenes, but before I digress...)
The following is some dialogue the story's initial script in a parallel universe:
Daimon Tarr: "Grr, where's my Alpo! Oh, my parallel-parallel universe counterpart cashed in on it."
Picard: "I say my dear chap, don't you need a good orthodontist? Or have you been acting like billy goat and trying to use those things as tin openers again?"
But anyhooey, nobody seemed to take the Ferengi to the next level until Armin Shimmerman came in for DS9 - by then, Trek was more than established, Shimmerman was one of the best actors to have played any Ferengi to date so it's an easy decision for him to make to come in... and the Ferengi are becoming a regular fixture. There's also a chance for more nuance and depth and that's when things get good -- note that the first person to recognize the potential for having more depth was due to Armin,
predominantly due to his input, and when an actor really digs into a role the end result is going to shine that much more and Armin for Quark certainly does. DS9 wanted to take a species that fell flat during their initial creation, but then improve upon them, even if they were still going to be used for comic relief moments. (For many reasons, DS9 used them better... not to mention, "Move Along Home" is unfairly and unreasonably derided, not that I've talked about it before but I'm not going to digress any farther.)
If anything, the early notion of how they eat humans was avoided and never brought back or deconstructed. That would have been an awesome way to take a plot point from "Day of the Dove", which had Kirk discussing propaganda to Mara about the Klingons believing humans had death camps and all that (but didn't) - now turned 180 degrees. Riker's comment was a bit out of left field, and a step downward compared to previously established Trek, what with this being season 1 and no character was fully pegged down yet...
So maybe that's the rub - early TNG had no focus and the end result is a mixed bag just waiting to be fleshed out.
So either which way, even with my nittynosepicks, I appreciate how their creation and initial usage still led to something greater down the road.