Went with A1 Excursion to Upper Mustang for a trek of two weeks in November.
I was more than surprised from the beginning of my adventure. Even arriving one day later as the rest of attendees I´ve been personally picked up from the airport by A1 (same for my departure, service level from an outstanding level).....
We´ve been guided trough an amazing nature from lovely guides, they spoke English very well and took care for all questions/remarks/lacks/comments/etc at any time. For the tiniest problem they´ve find a solution which made us happy at any time. Porters responsible for our luggage were more than reliable and guided us to find the best way - no matter what you need/ can manage - they´ve made the perfect decision.
Even every extra desire from us has been served accordingly. Being the first time on a trek like that, I´ve never felt lost or something like that, there was always someone taking care of me and the others.
From an organization perspective it couldn´t be better, flights have been booked in advance, all flights has been escorted to make sure we won´t run into problems, lodges were booked in advance, meals were prepared according our proposals.....every adjustment we´ve asked for - even an additional flight ha been fulfilled properly.
I guess it´s not necessary to comment on shills like being polite, friendly, reliable... The entire team exceeds that.
At the end of the day.....for everyone planning to go for a trek to Nepal I highly recommend A1 Excursion as your partner you can rely on.