There are some quick points written below, feedback, issues and ideas from my point of view...
Overall:
This distribution reflect a good overall work, but is needed a lot of work to achieve a big step forward.
Deepin Environment:
Desktop wallpaper is better placed in the control center, is much coherent.
Then a custom wallpaper option is needed.
The context menu of the dockbar is better is 15.2
I see some improvements in 15.3 but the overall experience is better in 15.2.
System Update:
An option for custom repository link could be very usefull, from some places, the default links are slow or unreachable.
Network:
Dns suffix option is needed in network settings, for a skilled user it can be set from terminal...for the others?
Deepin apps:
The Store doesn't work on enterprise environment (proxy,dns,firewall asset), like doesn't work system update. It needs some debugging for much improvement in this field, today this distribution is good for home computers and small business.
Advice:
To make your mark are needed some original ideas from fantasy, creativity and not only copying.
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Manual 
Overall:
This distribution reflect a good overall work, but is needed a lot of work to achieve a big step forward.
Deepin Environment:
I see some improvements in 15.3 but the overall experience is better in 15.2.
System Update:
An option for custom repository link could be very usefull, from some places, the default links are slow or unreachable.
Network:
Dns suffix option is needed in network settings, for a skilled user it can be set from terminal...for the others?
Deepin apps:
The Store doesn't work on enterprise environment (proxy,dns,firewall asset), like doesn't work system update. It needs some debugging for much improvement in this field, today this distribution is good for home computers and small business.
Advice:
To make your mark are needed some original ideas from fantasy, creativity and not only copying.