I bought a 2013 AF 990 in February and the only issues I've had have been the use of inadequate hardware to hold trim items on. For example, the cabinet doors use tiny screws that are easily pulled out of the wood. Another example is that the shower head cradle was screwed directly into the fiberglass, which never works that well unless epoxy is used, and sure enough it stripped and pulled out.
Obviously both of these things are quality issues, but are super easy to correct. When I was looking around at TC's I looked at all the other brands as well, and the only one I saw that seemed to be of higher quality was Northern Lite, and I've seen complaints about those as well so nothing is ever going to be perfect. Remember that the usual selling price for a new Arctic Fox TC is less than a lot of other brands, so a few compromises are expected, and even so I feel that it's a great value.
The biggest design issue I have is the use of carpet on the ENTIRE slideout floor, which is just crazy. I would much have preferred linoleum, or at least better carpet instead of that incredibly cheap shag. Since it is covering the entire floor, it's also in the storage compartments. Getting it out of there will be hard because I'm pretty sure the structure was built on top of the carpet.
The basement fan was not ducted so efficiency is probably not great unless you correct it like I did. It's hard to say if it's inefficient enough to cause a problem if you just left it alone though. I don't think the vast majority of people would ever encounter conditions where it mattered.
As a recent buyer coming from the world of worse quality TT's, I'm super happy with it. I think someone coming into RVing for the first time buying one might be a bit put off, but all of us that have owned RV's before know the drill.