Review (5/5): great if you know what  you are doing
I think these are a great idea. I need to practice more with it and adjust the size of the lashes. My initial attempts were a little messy and it is strange having the weight on your lids. I never could get the hang of the glue on lashes, so I was hoping these were easier. If you regularly use liquid liner, these will be easy for you to use. The hardest part is getting the liner on smooth and straight. Once it is on, the lashes stick very well to the magnetic bits in the liner. Also, they come off fairly easily when pulled. Potentially, it means you could accidentally pull them off if you play with your lashes or rub your eyes. But they do stay on well, without touching.
The lashes are a standard length, so if your eyes are smaller or larger than standard, you may have to adjust - more for smaller than larger. If you've never worn lashes but have always wanted to try, this is a good way to start.