On the down side,
1. They are pushing cloud connectivity and telemetry very hard. Not sure if you can opt out any more?
2. The local control panel tries to be everything to everyone and as a result sometimes doesn't surface features you want from the underlying programs. They package a TON of things and don't really have time to surface all the config. I'd rather they package just NAS things well and leave the rest alone.
3. Their packaging is largely opaque, compiled code instead of linux standards, possibly for obfuscation, and it doesn't always play nice eg if you install your own VPN because the UI doesn't work for you, then it may step on you so you have to do it their way anyway.
To be fair, it's not like this software is going to be really complicated. At the end of the day it's just a web front-end to more mature tools. I don't think it's going to be too difficult to compete.
I wonder how mature Ugreens software is comparatively.