This is only a partial review with a particular perspective. I borrowed one and evaluated it as a FLARM display. In theory it sounds great because of the large display. However, I would not recommend the Nano 4 as the primary flarm display because
1) Very reflective display makes it hard to read. If I could upload a digital photo you would be convinced. That is enough imho to make it unworthy? of a primary flarm display.
Other consideration is the cost effectiveness
2) It's much more expensive than something like the small LX Nav Flarm LED+ because of the following:
a) You have to keep it in the Flarm display page since it will not automatically switch to the Flarm page if there is a potential collision. So it makes many of the other functions useless because you don't want to be on another page when a potential collision is going to occur.
b) It becomes more expensive since you need to buy a special adapter cable to connect it to the Flarm to get the flarm data. On a relate note, the FlarmFusion has BT but the Nano4 can not connect to the FlarmFusion via BT.
If you are using the Nano 4 for other reasons like the navigation, IGC flight recorder, etc. etc. it is probably pretty good as long as the reflective display is acceptable to you.