We stayed at TdI last April, and it was terrific. The Tripadvisor reviews are accurate, and it is an amazing bargain points-wise. It's great for exploring the Sacred Valley (e.g. Ollanta, Pisac, Moray, etc.), but not that convenient as a base for Cusco. I think most people split the stay, with a few nights in Cusco and a few at TdI. I would definitely recommend spending at least a night in the Sacred Valley, as it has a very different feel.

If you do split your stay, you might consider going to the Sacred Valley first, and then hitting Cusco on the way back, if you are prone to altitude sickness. We did the reverse and regretted it, as it would have been easier acclimating to the lower altitude of the SV and MP.