Just before I start, I don't usually leave feedback on anything however with this I simply had to.
I received my Apex today, all I can say is, this product is Amazing, I've been a Xim user since the Xim 3, and have been recently using the Xim 4 for playing on the Xbox One X on COD WW2. I always thought the Xim 4 was very good as a KB/M adapter for console, however this is on another level.
In terms of the raw performance in game, in COD WW2 specifically the movement feels very responsive, just like playing a PC game, It's something I noticed straight away. Any floaty / input lag movement which was present on the Xim 4 is now gone. This is certainly down to the new 1000hz polling support on the Apex. I tested it on 12K DPI on my Logitech G Pro, the same as I used on Xim 4 and the difference is night and day. I also played around with the smoothing setting on the Beta firmware to help with the jitter introduced with the 1000hz polling and I found '10' was a good value to remove the jitter, but I also found it helped to track targets with the aim assist as an added bonus. I find aiming 10x better on this than on Xim 4 which has increased my enjoyment of gaming by far, and this is only day one. Some guy on the opposite team on WW2 messaged me first game to say he reported me to XBL and that hasn't happened to me in this game until now!

I do like the new Apex app a lot, I was very impressed that it detected my keyboard brand, I use an A4 Tech Bloody keyboard! there was no way I was expecting that, as I know that not many Xim users use the bloody range, no idea how you guys did this but, bonus points!
The only thing I could suggest for improvement in the app for me personally, would be to add support for 3 decimal places for the Xim sensitivity if possible, I am very picky with the sensitivity I use and I always wish I could test a value in between two of the 2 decimal place sensitivities available in the app. It's probably because I use 12K DPI so the Xim sensitivities have greater differences between values, I could go lower with DPI but I like the feel of high DPI with the Xim.
Also I found it a little bit difficult to tap in the box to change sensitivity, maybe the box could be a bit larger, could just be me.
All in all, brilliant product and very good value for money. I look forward to seeing what the Xim team will bring in the future and am very glad to be part of this community