I've been using this duo daily for 3 weeks now, and I have seen enough improvements to make it worth my while. Admittedly, my nails were in a very poor condition to begin with; brittle cracks went from the tips down about half way to my nail bed for my thumbs (not through to the skin, but in layers). They were very filmsy and could bend easily (and snap if hit fast).
Both of these products will go a long way. After daily use for 3 weeks I've barely touched either. The bristles of the brushes are both quite coarse and made of thick plastic strands, but not a biggie for me as the polish and oil glides on easily. The strengthener dries quite quickly which I really like. I'm not so much of a fan of the oil though because it feels greasy and I have to wipe away the excess off my fingertips before moving onto anything else.
I'm not blown away with but am happy with the results. I think they're mainly due to the strengthener rather than the oil. Although there is still cracking on the top of one thumb nail it doesn't go far down, and the other thumb doesn't show any cracking at all. I know that having the strengthener has saved several of my nails from breaking since using it. They are longer, and strangely enough stronger but to different degrees. What I do not like is that the bottoms of underneath my nails are see through (something that happens if I wear polish but hadn't expected for a see through strengthener).
All up I wouldn't buy the duo but having the strengthener as basically a constant/regular treatment for my nails seems like a good option. Especially given how long one bottle will last me.
I was really excited to be selected to trial this range. Pre-pregnancy my nails were awesome, but two pregnancies back-to-back coupled with HG meant my nails are now brittle, flakey, and breaking left, right and centre.
I had high hopes for the Revitanail system. Sadly, the formaldehyde in the polish, coupled with it flaking off all the time; and the weak oil, meant my excitement quickly faded.
Yes, my nails were slightly stronger, and they haven't flaked. But, they have chipped. I haven't found my nails are stronger without the polish though - so they haven't strengthened in themselves, the polish gives them the strength.
The system is also tedious (repeat for 23 days then a break, then start again).
And, let's repeat again so it's clear. Formaldehyde is present. It doesn't state at what concentration but because this is a system you're using over many, many days, you're getting exposed to it every day.
Tips: Read the ingredients and make up your own mind.