I just returned from Tateyama. If anyone's thinking about going then be warned - there's still over a meter of snow on the ground! Make sure you bring crampons and an ice axe if you're climbing any peaks (especially for Mt. Tsurugi). Mt. Dainichi is fairly free of snow, but you'll still need crampons to get up to the ridge. Raicho-daira and Tsurugi-sawa campgrounds are completely buried. The snow makes for wonderful scenery, but I'd wait until mid-August if you're under-equipped.