I've had my hair cut at Lain Guy four times now. The first time was by M. Guy himself, as I'd won a free haircut from gochengdoo.com. M. Guy is French-Cambodian and can provide services in French, Cambodian, English and Chinese! If memory serves, he told me that after leaving France, he spent several years in Shanghai and Beijing before coming to open his own salon in Chengdu.
Anyway, after the first haircut, every other time my hair has been cut by Yuming as, sadly, I just can't afford the amazing M. Guy! No matter, as I have not had a single bad haircut there.
The place is nice, clean, and I appreciate the understated decor when so many salons in Chengdu are so frou-frou. They actually sit you down and do a proper consultation on your hair before washing! Also, I like it that I can have a friendly chat while I'm getting my hair cut if I like, but it's no big deal if I'm quiet. Everybody who works there is friendly and they do anything and everything they can to make their customers happy. I've seen them deal with some very picky clients with absolute patience and professionalism.
It's a bit pricey, but I was already going to a pricey salon near Chunxilu, paying over a hundred for a haircut. I hear from friends that prices for color are definitely up there compared to other salons, but they've mostly been happy with the results.
As an interesting aside, M. Guy said that he has experience cutting natural and treated black hair and is also happy to offer straightening and perming services if the customer brings the supplies (which can be brought from abroad or purchased on taobao).
The only small criticism I have is that the hair washing service is just not as good as the typical Chinese hairwash (hence 4 stars). Why not have the best of both worlds and offer a nice long hairwash-massage? It would be so nice to have both a great hairwash and a precise made-to-order cut.
In any case, I simply will not go anywhere else to cut my hair. Not only is it the best place in Chengdu, it's probably the best place I've ever been anywhere, especially for the money. I wish I could get my hair cut by a Parisian stylist back home, but it'd surely cost hundreds!