Yes I have noticed they sell out quickly as it took me a week to finally purchase one after some research. There are those flaws with the lens but in all honesty for what I use it for the problems were not bad enough for me to want to return it. I definitely really have enjoyed shooting with it. If you decide to get one when you find it in stock, I say try it and if it doesn’t fit your needs then you can always return it. 🙂

I just bought this lens for EF mount so I can use it on my Canon 6D and adapted on my Fujifilm cameras. This lens is the cheapest 500mm prime lens in history (at original retail price, as far as I know) that it doesn't have the build and image quality of toy lenses. I can confirm that it does have CA wide open (for a reason I noticed it more on pictures from my 6D than on the ones from my X-T2). However the CA is really not as bad (the worst CA I have seen is from the EF 75-300mm), and better yet I have not seen Longitudinal CA which is hard to get rid in post. It is a lens that its better to be used with a tripod, handheld shots are quite the challenge. I see this lens as being the entry gate for bird photography for newcomers, and what excites me the most is the hope that TTArtisans might release a new version of the lens that is faster (f5.6 hopefully), sharper, with IS and AF in a couple of years.