I replied in the other Holosun thread, but from what i heard they are updating the 509t with better more clear glass and a new circuit board that lets you have the dot, dot/circle or just the circle. Should be out in a month or two.
Unfortunately, this can be said for the entire Holosun lineup. There are huge variances between samples of the same model line.
Having said this, i've found the distortion to still be better, even on the worst samples than anything Trijicon has ever put out in the RMR lineup. In my opinion, Trijicon glass in their red dot optics is absolute garbage. The exception to that opinion being the SRO. The SRO to me is extremely clear edge to edge and the magnification is about as close to zero as you can get.
In speaking to somebody fairly close to the source, I believe this to be accurate. Definitely a lens redesign. Probably a fringe benefit for Holosun of getting to call it an X2 and making the nomenclature line up with the rest of the pistol optics. For most folks this will be a great opportunity to get a cheap 509T. Hopefully the green dot 509T gets here soon.
Optics Planet has HE509T for $289 if you use their coupon code. I think the 15% off code runs until the 30th.
I mean there has to be a new version coming out for the prices to be getting this low.