Here a short review after i get a working SD-Card to try my UK1541.
Pros:
The most games with fastloader work like a charm.
Also i think the quality of the UK1541/remote control/cables are absolutely ok.
For this price it's a recommend device!
The Problems:
I have always a white screen if a CR2032 is inserted.
I can’t mount some d64 images like California Games from ESI(The image work with sd2iec/vice).
The message „Can’t mount“ didn’t disapears if i mount another d64 image.
Edit + picture:

Barbarian is already mounted.
If i use the 'original' filenames from „some d64 collection“ the UK1541 can't read the SD-Card.
This is not a problem with the fragmentation.
Suggestions:
I think the characters should be bigger on the small display.
Remove the logo and the content on the mainscreen - it should only show the d64 images.
After mount a image it should show (only) the content of the d64 image.
The joystick input should be debounced.
With a lot of joysticks it is very hard to handle the UK1541.
However i like the UK1541.
Thanks @ kisiel.
Plz forgive me for my bad english.