I wanted to post a review of a tour I did last summer with Manu Explorers. I booked this tour without seeing many, or really any, reviews of the company. After our successful trip, I want to spread the word of our positive experiences with them. The company was great to work with, our guide (William/Guillermo) was very knowledgeable and spoke great English, and the food and accommodations were good. If you are set on going to Manu, I would not hesitate to recommend them.
There were a few concerns we had about our trip, although not directly related to the company. We originally wanted to go in over land and fly out. Unfortunately, all air flights out of Boca Manu got canceled. Wilbur (the owner) was very honest and upfront from the very beginning about this possibility, so I have no complaints about this circumstance from their end. However, I would highly recommend, if possible, taking the option to fly out of Manu. Otherwise the boat/van back to Cusco is interminably long. The extra money for the flight out is very very worth it.
The other concern is whether you should even go to Manu Reserve at all. Looking back, I probably wouldn't do the same trip again. I would only recommend the Manu Reserve for those of you who are true jungle nuts. Part of its appeal may be its remoteness, but that also means you spend much of your time (two full days) just getting in and out. I can compare this experience with being in the jungle on the Osa Peninsula in Costa Rica, and I felt like I had just as positive an experience in my 1 day jungle tour, and also had the variety of other activities that the Osa allowed. With the 6 day Manu tour, you are somewhat captive to the limited hikes that the guides can provide, because you don't really have the option of doing anything else. In the end, I would probably have preferred to just go to one of the jungle lodges out of Puerto Maldonado, which would be less of a time and money commitment.
But like I said, if you are committed to going to Manu, do not hesitate at all using Manu Explorers. A great company to work with.