I like niche bikes because they are unusual, one of a kind, and a conversation piece. edit: I am talking about motorcycles, not Uncle Ernie.
Unfortunately, many niche bike companies teeter on financial ruin. We have seen Buell go belly up recently. Ural is but a shadow of the heavy producer it was a decade ago, and there is always talk of financial instability. Moto Guzzi seems to be going out of business more often that the local furnature store with it's permanent "going out of business" sign in the window.
While Enfield is definately a niche bike, it is only a niche in this country. Many are sold in India, and it is a strong company. RE's big weakness here in the states seems to be the dealer network. There always seems to be a dealer on the way out. Fortunately, we have some strong dealers to take up the slack.