One day Sikkim's far north could be amongst India's great visitor attractions with its array of pristine mountainscapes, yak-herding traditions and trekking potential. However, for the forseeable future, military sensitivities mean very tight restrictions limiting the experience to mostly out-and-back excursions where virtually all you see is what you can glimpse from a jeep window.
This doesn't appear to worry streams of exhausted Indian tourists whose vehicles rush along the tiring, narrow lanes. And to glimpse the glories of the Yumthang Valley it is still worth jumping through the various bureaucratic hoops involved. You'll have to join a tour to get the permits, though that's easy enough to organise in Gangtok the day before departure, so long as you're not travelling alone. To do things more slowly, organise the permits and tour in Mangan.