Over the years, I've used a ton of Garnier products, especially hair products, and I've liked some and hated others. But let me tell you, their last two lines of serums have been game changers for my hair.
I have wavy hair that ranges from 2a to 2c, and I've realized that the CG method will probably never work for me because my hair needs silicones or else it tangles and gets damaged like no other. The Garnier serums are like all others in the market (like the high end Moroccan Oil to the low end Suave serums) are mostly silicone serums with just a dash of the oils they advertise on the bottle; however in Garnier's case, I do believe they have a bit more of the oils than other pricier or cheaper brands. I used the Deep Nourish variety with the Cupuacu and Brazil Nut oils, though I imagine the other two in this line would perform pretty close to the same way.
I usually use a cream type leave in conditioner underneath this product, but even when I don't, I get good results. My frizz is significantly reduced without weighing my hair down, and my hair seems more resistant to tangling. My hair also seems to dry faster using this. It smells very melon-y, quite different from the Sleek & Shine Moroccan Argan Oil treatment, which is more incense-y. I think the performance of the Moroccan Argan one is about the same, though I think the Marvelous Oil is a bit lighter. If you're debating which of the two to get, I'd recommend the Marvelous Oil because you get 2x the product for the price (around here, the Argan one is $6-7 for 3.75 oz while Marvelous Oil is $5-6 for 6 oz.), and for some reason, the Garnier sales sometimes don't include the Argan oil one. Anyway, the most important thing is that it makes my second/third day hair more resistant to tangles. On days I don't wash my hair, I still use a detangler, but I use a lot less because this is on my hair from when I washed it the day(s) before. It's super economical because I only use it on my wash days, so the container lasted over a year.
The one complaint I have is the packaging. It looks really cute, and is mostly travel friendly. However, the pump gets slippery after using the product, and I scratch my hand as it slips down the rough neck of the bottle. Also, because it's a weird shape, I can't invert it easily to get the last bits of product. I just ran out of it and am currently using another Garnier product (a cream styler), but I'm hunting this or the Argan oil serum down again as soon as I'm done with it.