This is long overdue. I tried to get TripAdvisor to list them, so that I could review it in the right place, but failed.
I started with ~ 3 companies who had great reviews on TA. They all charge the same for the basic packages, as these prices are government controlled. However, if you want to upgrade hotels, each has a different price, even for the same hotel. Heavenly Bhutan Tour company (HBT http://heavenlybhutan.com/) had the lowest prices for the upgrades.
We worked with Menuka, who was very very responsive and a pleasure to meet in person. We stayed in Bhutan for 5 nights and 6 days staying at Le Meridien, Thimpu (2 nights), Drubchu Resort, Punakha (1) and Hotel Zhiwaling, Paro (2). They did get us upgraded to a very nice full suite at Zhiwaling.
Our driver was Om, and the guide was Sajan. They stayed with us throughout the trip, including the hike to the Tiger Monastery, which was a challenge for me - but worth it!
As you are paying enough, I recommend that you select the restaurant of your choice versus the guide recommended ones.
Overall, highly recommend!