I have used Marqthon threads almost exclusively on both my DSM and my Milly and have nothing but good things to say about it, have never had any tension issues, exceptional delivery 2 days here in Northern Ontario, Good pricing.
In my Milly, I usually use Cotton Look polyester 50 wt in the bobbin and either 40 or 50 wt in the top. I have used the cotton 50 wt with no problems.
I have not tried the specialty threads in Milly but have used them for my DSM and have had no problems, friends with embroidery manchines use them exclusively.
Hope this helps