I don't know if I could call myself a lunatic exactly, but it has become one of the loves of my life. So far I've played 6, Embodiment of Scarlet Devil, through 9.5, Shoot the Bullet, including 7.5, which was the first Touhou fighting game. Touhou was my first encounter with danmaku, and it really is addicting, although of all the ones I've played I still havn't gotten my first 1cc, well, I've gotten a couple on easy.... I'll second Perfect Cherry Blossom as a good one to start with, it's very pretty and one of the easiest to get extra lives in, but personally I found the difficulty level of Phantasmagoria of Flower View to my liking as well.
As a side question directed at Gensokian and others who are familiar with the series: who would you say are your favorite characters? Just choosing three or four... mmm, I'd have to say mine are Remilia Scarlet, the vampire who "always leaves some food on the plate", Marisa Kirisame, the "ordinary" black magician, who's antics and conversations with bosses make me grin, Cirno, the clueless, tomboyish ice-fairy, and Shikieiki Yamaxanadu, the judge of the afterlife who berates all the other characters with well intentioned lectures on how they should change.