I upgraded one of my pc (used for testing) and it worked. No errors I think.
I had to erase some programs and some old linux-headers (too many, too much
space) because root partition was 3/4 full.
The upgrading process needs at least 6 GB. The standard root partition is 10
GB by default (no LVM option). I think it's too small.
Package download didn't take so much time thanks to my net provider...
I don't know if there were upgrading errors...no messages at all.
Now I have a GNOME/Mate desktop, which is quite different from Trisquel 8
Mate installed in other PC...