I bought this primer to try out since it's readily available in the North American market. My previous experience with mascara primer / bases was Kanebo (Kate) which was excellent but not easily available - my wish was to find something relatively inexpensive and easy to replace. Unfortunately, the Clinique Lash Building Primer did not live up to the expectations.
My mascara application routine is normally as follows: curl lashes with Shiseido curler, apply mascara base (this part is optional depending on the look I'm going for), let base dry, apply mascara, and then comb through lashes with Tweezerman metal lash comb. This primer has normal bristles and a small brush which does make for easy application, however, as many others have mentioned, this base does not hold a curl at all. As soon as I apply the primer, my lashes start to uncurl themselves, thus wasting the effort of curling them with a lash curler to begin with. I've also tested not allowing the primer to dry before applying my mascara but it made no difference and actually was more of a pain to cover the white colour of the primer while it was still wet. Also, the formula is quite wet and takes a while to dry before I can apply my mascara. I didn't notice a huge difference in length when using this primer, but it did make my lashes look more voluminous. I also did not see a significant improvement in how long my mascara stayed on without smearing / flaking. One good use I found for this primer was layering under waterproof mascaras which tend to irritate my eyes if I wear them alone - when I layer a primer, it helps to lessen the irritation, for some reason.
This cost $17CAD, which isn't exorbitant and I purchased it during a Clinique gwp event along with something else - so I guess all was not lost as I got some nice samples to try out. It does not contain very much product at 4.8g per tube - overall, I would not recommend this product and would not repurchase.