We hiked the Inca Trail with United Mice back in November 2012. They were one of the few companies that was on top of their correspondence, but the organization stopped there. We were instructed to come to their office at 1pm the day before the trek to go over the final details. When we arrived at the address we struggled to find their front door. Once we eventually found it, we were greeted by a non English speaking employee who told us that our English speaking guide was on his day off. This should have been our first indication that they had forgotten about us. Four hours later we were able to meet our guide and go over the details of the trip. We booked the 4 day hike, but were told that the camp site for the third day was full and we would have to hike the entire trail in 3 days and stay in the town of Aguas Calientes on the third night. This meant not arriving at the Sun Gate at sunrise, three times as much bus fare up and down the mountain (at our expense), and a night in the worst hostel in Aguas Calientes (generously paid for by United Mice). The guide was nice enough, but fell short with his knowledge of the history of the area and lack of sensitivity to the needs of his group. Hiking the trail in three days was a fairly aggressive pace, unless the guide decided it was time to stop and talk on his mobile phone. Other tours got to have an easy third day and hike to a beautiful waterfall and explore some ruins at their leisure. As one other post mentions, they booked us on the cheaper 6:45pm train back to Olantaytambo without consulting us. This meant that we missed the beautiful scenery of the Sacred Valley and we got back to Cusco at 11:45pm without transportation from the bus stop to our hostel.
The positives of the trip were the support staff and the equipment. Our cook was fantastic and prepared amazing local dishes for us at every meal. The porters were great and were also treated better than porters from other tour companies (porters from one other company didn't even get their own tents and had to sleep on the floor of the communal toilets during rainstorms). The tents and mats were old, but withstood very heavy rainstorms.
Overall we would not recommend United Mice. The disorganization and the feeling that they completely forgot to book things for us from campsites to hostels to bus tickets left us feeling cheated for the high price we had paid ($600 each with inflatable camping mats, but without a porter to carry our packs). Whichever company you do choose we would advise asking for a detailed itinerary by email before your trip to make sure you know what you will be getting.