There is no design flaws, or problems!
It is a Mossberg 500 in almost every way. In fact some of the new 500's even have the one piece plastic forend as well, which was really the only complaint some had about the Maverick 88.
The only other real difference is the safety is a cross bolt in front of the trigger, whereas the Mossberg is a tang safety on top of the receiver. For me this is actually better on the 88 as I use a pistol grip alot which would make using the tang safety on the 500 near impossible!
I have owned mine for almost 3 years, and have 3 different barrels for it. It accepts any Mossberg 500 barrel and I have the 28 inch vent ribbed barrel with removable chokes, the 18 inch smoothbore, and a 24 inch deer barrel! It has seen thousands of rounds of all kinds and has been 100% reliable!
The only reason I would say buy the Mossberg is that if you plan on using it for multiple purposes like I do, and want the other barrels, you will get a better deal going with a Mossberg 3 barrel combo than if you buy the Maverick 88 and all the barrels seperately.
I went with the maverick because I started out only shooting at the range and was more into tactical stuff, so the 18 inch barrel and crossbolt safety was better for adding a pistol grip, for range fun and backpacking stuff.
I then got into trap so bought the 28 inch vent ribbed barrel, and then started hunting this year so had to buy the deer barrel as well.
Buy with confidence, if you do choose the Maverick 88! I beat the #### outta it and don't worry about it at all, and it is nice to just be able to not worry about a gun. It is strictly a tool, but one that works very well, and is a great deal!