I purchased this product just about a month ago and I love it. I make my smoothies daily and it works great. My only problem is, because I have Rheumatoid Arthritis my hands don't always work well so I have difficulties with the handling of the glasses.
I love that this unit actually breaks up the seeds found in blueberries! Before I used to find them in my teeth so this is a big issue for me. The only suggestion I have is to make the outside of the cup have some sort of texture or ribs to make it easier to grip to be able to unscrew. The older generation like me or those with small hands needs a bit of help. Since these cups are rather large around, they are hard to open if they are sweating from cold ingredients or if there is a suction due to warm ingredients being blended. Other than that issue, I can't live without it. Great product.