I tried out the Jawbone UP band in its first generation, and it was a disaster. The smartphone apps that were designed for it were severely lacking; for example, food items had to be (slowly) downloaded for every meal you wanted to input. My first band stopped syncing after 10 days, and two resets did not fix it. Jawbone sent me a replacement band, but it was the wrong size. They finally got me the correct band, but it would not sync at all.
As if that wasn't enough to trash the whole experience, the online seller I had initially purchased the UP from would not process my refund. This was due to me previously following Jawbone's instructions upon the first RMA return, meaning that I had already sent them the original packaging, etc. it turns out that they won't accept returns from their channel partners without the packaging, so this put my seller in a pickle. After several emails and phone calls I was not able to straighten any of this out, and ended up charging the purchase back via my credit card issuer. I know that stuffed the seller, but I feel that the issue lies purely between him and Jawbone, so I will let them figure out it.
When this is someone's first experience with wearables it is not hard to understand why their adoption and usage rates are low right now. I will not get into another wearable until both the manufacturers and their products mature.