I am not sure when and where I got these Teint Idole Ultra Wear anymore, but Lancôme foundations are always good in my experience so I enjoy trying them out. It might just be that the shade is not the right one for you, but for a sample you can see the finish, consistency, if you are alergic, etc. If you like it, then you can go back and see if there is a shade that fits you well. So, in general, I find this type of samples very useful.
The packaging of the sample and the sample size were good. No complains there. The consistency and the feel on the skin is very light, feels like your skin and looks like your skin. I really liked it. I would say this is medium coverage but buildable to a bit more if you apply another layer in the parts where you feel you need more coverage. It was also long lasting, which is always good, specially if you want it for a party, or you use it for work. It states 24 hours, which I do not think anyone needs.
Would I buy it based on the sample? Yes I would. My favorite foundation is Parure by Guerlain, and this comes very close.