I prefer to organise trips myself without the use of a travel agent, even going to Myanmar I researched flight schedules etc and tried to book everything myself. However, I found it's not easy to organise these things yourself in Myanmar, and caved and used an agent!
I ended up contacting three travel agents I found recommended on TripAdvisor forums, two replied. One of the two was bumped to my spam folder and I didn't find it till some months later. However I am very happy we did go through One Stop, the only agent I received a reply from in my inbox. They responded very quickly (within 24 hours) having looked at my suggested itinerary and made some very helpful suggestions to reduce the amount of time in airports, reduce the cost by about $100, and maximise our time sightseeing. The other travel agent gave a quote for my requested flights but didn't put in this extra effort to help plan the best trip possible.
I organised most accommodation myself but when I had some trouble with my booking in Ngapali I asked the travel agent to try to book a hotel for me. Unfortunately the one I was interested in was fully booked, but again she went above and beyond suggesting a few other places of similar quality and cost nearby that did have rooms available.
We had absolutely no issues on arrival or through any of our trip. All tickets and hotel vouchers were given to us and well organised to stop us getting mixed up. The cost was similar or slightly lower than the costs I found when looking at booking myself.
I would highly recommend One Stop to anyone visiting Myanmar, especially with a complex multi city itinerary. Our agent was Kyi Thar Myint, 09-31044160, firstname.lastname@example.org.