Pros
Overall, if you work for a good store with a great Store Director, you'll probably stick it out and enjoy your time. You typically have a great team of people to work with, although clique-y at times (Store depending). You get a lot of free makeup, skincare and fragrance. If you're a starting makeup artist, it is recommended as you learn how to work with all skin types, tones, textures, face and eye shapes, and a whole whack of personalities.
Cons
If you are an advanced makeup artist with more than a few years of experience, and you want to advance yourself, this is probably not the place for you. To become an elevated cast member, senior artist, lead, or specialist, you definitely have to drink the cool aid and lose your own personality, to mold to a set of criteria which it Sephora approved. Amazing skill set? Tenured makeup artist? Refuse to force people to buy stuff they don't need? You won't be selected as a Senior Artist, as its about sales. My Store Director was verbally and emotionally abusive to her cast members, which made the experience awful. On top of that, you are constantly told you get so much $$ worth of makeup for free to compensate for low wages but I soon found out my landlord doesn't accept Bare Minerals powder as rent. Favourtism is rampant, and although I never had a problem, I have seen people who had been so poorly treated and given horrible schedules, as well as constant sarcastic and backhanded commentary...unbelievable. This is not the picture of every Sephora, mind you, but many.