So why all the sass-mouth? I mean, if there was concern about the airlock system being subpar or it varied wildly in temperature or ... or some other concern that'd be one thing. Even if it was simply not as good as another system. But the "If I met Mr. Beer in alley I'd kick its ass" and "you don't want that piece of crap" really do not seem justified.
People often have opinions that have little or no foundation in fact. You'll find this holds true in many spheres and doesn't only apply to the Mr Beer fermenter.
I think there are also a number of things that lead people to view Mr Beer negatively.
It's inexpensive and it says you can make beer in as little as 14 days, so people buy it. They read the instructions and see that they can bump the alcohol content by adding some plain white sugar (and/or honey and/or maple syrup, etc). They also see the temperature range as being between 68 and 72. The old refills included 2 grams of yeast (not enough) and Booster.
They then brew up the refill that came with it, dumping in a bunch of sugar to increase the alcohol content. They stick it in a room that is about 70F and leave it for a week. Then they bottle it, wait a week, stick it in the fridge for a couple of hours and drink the beer.
With the old refills, the Booster already bumped the adjuncts too high in relation to the malt. And there really wasn't enough yeast to do the job properly. There was enough to ferment into beer, but 2 grams is seriously underpitching. The room was around 70, so during active fermentation, the brewing temperature probably got above 75. And they added simple sugar on top of the already too high adjunct level.
So what happened? Too little yeast led to lots of ester formation and possibly to underattenuation issues. The high temperatures led to more esters and possibly to fusel alcohol. The high level of adjuncts produced a lot of acetaldehyde and a thin end product.
If they had given it more time, some of these problems would have faded or even disappeared, but they read the marketing materials and wanted beer in as little as 14 days.
When they drank it, they drank straight from the bottle or poured it one glass at a time. Combined with the lack of time, this meant that they ended up drinking a lot of trub with their beer.
But they DID make beer, so they were encouraged to continue. They then visited a homebrew store, determined to discover how to make GOOD beer. At the brew store, they may have run into somebody who doesn't know much about Mr Beer, or somebody who heard that it makes bad beer, or maybe even somebody who went through the same steps he did, ending up with a sub-par beer.
So he walks out with an Ale Pale, a glass carboy, a stick-on thermometer, an all malt recipe, a package of yeast with enough yeast to do the trick (or maybe a vial of liquid yeast, a stir plate and flask and instructions on how to make a starter), a hydrometer, a siphon, etc. He also has clear instructions on how to brew it, how long to ferment it, how long to let it sit in the bottles and how long to let it sit in the fridge.
He goes home, brews it up and 6-8 weeks later, takes a taste of the beer. And it's really good.
So he concludes that the problem was Mr Beer.
In reality, he changed EVERY SINGLE THING that he did the first time around. The problem wasn't Mr Beer. The problem was that he didn't follow the proper processes to make good beer.
Some of the problem lies with the Mr Beer instructions and marketing. It's true that you can make beer in as little as 14 days. But it takes longer to make good beer. I think they have a comment to the effect that the beer may improve if given more time, but they don't really stress it. And they have a chart that tells how much alcohol various ingredients add. I think they may mention that you should keep your adjuncts below a certain amount, but its importance isn't really obvious.
Can you make bad beer with Mr Beer equipment and refills? Absolutely.
Can you make good beer with Mr Beer equipment and refills? Absolutely.
It's up to you.