I didn't start with Mr. Beer, but I was on a brewing hiatus and was coincidentally given a Mr. Beer kit for Christmas 2014.
After spending some time on the Mr. Beer forum, which I found to be a rather odd place where some not-exactly-100%-correct advice is taken as gospel and defended rather militantly, I noticed that some are of the mindset that using Mr. Beer products is somehow different from "mainstream" homebrewing. For example, when I was new to the forum I was chastised by a senior member when I mentioned that I had boiled my hopped extract. I was informed that I had ruined my beer by doing so. Seriously. There were a number of real head-scratcher threads, but the final straw for me was a rather heated argument I had with a noob over conditioning time. Maybe I got off on the wrong foot when early on I told everyone that, in addition to boiling the s*** out of my cans of Mr. Beer light lager extract, I had used them to make an ESB and a saison. Whatever.
Anywho, "Mr. Beer brewing" basically consists of 1. A uniquely-shaped small batch fermenter (which works well), 2. kits from Coopers which brew 2 gallons of beer, and 3. the use of plastic screw-top bottles and carb drops. Other than that, you're making beer just like every other extract/partial mash brewer.
Don't get me wrong. I think the Mr. Beer system is a good product for the beginning brewer, or one who is happy doing small extract batches and/or wants to try small partial mash recipes. For me it was nice because the fermenters were small, and until recently I had serious limitations on space. I never used the carb drops or plastic screw-tops, not because I had a problem with them but simply because I preferred batch priming and glass bottles. Once I had used up the Mr. Beer extract I had accumulated (thanks to the clearance aisle at Target), I went straight to 2.5 gallon all-grain batches that were fermented in Mr. Beer LBKs.
Does Mr. Beer offer any advantages over the more conventional homebrew kit I bought at Price Club (aka Costco) 22 years ago? No, although some of Mr. Beer's features might be preferable to some brewers. Ymmv.
Mr. Beer products are fine, and I wouldn't tell anyone to avoid them. However, I have a few words of advice for new Mr. Beer brewers who might be reading this. First, don't think for a minute that you have to stick with Mr. Beer kits. There are bazillions of great recipes available for free online, plus formulating your own recipes is fun and easy. (You should be patronizing your local homebrew shop anyway.) You can make just as good or better beer without using Mr. Beer kits, so don't be afraid to branch out if the spirit moves you. Second, do not rely solely on the Mr. Beer forum for homebrewing advice. No offense meant towards members of that forum, but in my experience there are better options available. This site and the AHA site are outstanding resources, for example.
Cheers!