I think their fragrance oils are pretty good overall, although there are some hit and misses with their FOs just as there are with any other FO supplier. Their FO prices are often higher per ounce than prices for comparable FOs from other suppliers. But there are some FOs they have that aren't offered elsewhere. Also, if you want your FOs in glass bottles rather than plastic, you'll be happy with MMS.
I wish they allowed users to provide reviews. I also wish they would tone down the romantic overblown descriptions they use to describe fragrances -- it's really not helpful and can even be misleading. I'd prefer to see them give more tech info including IRFA guidelines, advice on acceleration, discoloration, and sticking power in soap, suggested usage rates, etc. (Nature's Garden is one of the leaders in that respect.
MMS does an excellent job of packaging an order. I also like that I can get a wide variety of supplies, ranging from specialty fats and oils to basic lotion making supplies to containers and bottles to colorants and fragrances. All have been good quality.