My family and I stayed out Juniper Springs the week between Christmas and New Years, arguably their busiest time. The hotel was at 100% capacity but we never felt like our needs weren't met. The hotel staff was very attentive and knowledgeable about both the area and the ski resort. You can buy lift tickets and rent ski equipment from inside the resort, which is huge, if you've ever seen the lines at the lodge.
We parked our car in the underground parking lot and never needed to get it out until we checked out. The hotel has a complimentary shuttle that operates everyday and will take you wherever you want to go, although it's on a first come/first serve basis.
All in all, we feel like we had a great first experience in Mammoth, thanks to Juniper Springs.