My cat Mitsu has been using the 14 day. Getting a correct install seems to be tricky. The first sensor we had wasn't installed correctly so we had to turn right around and by another. That second one has been working great for a week now.
What's great and others don't seem to realize, is that you get continous monitoring. It gets a reading every 15 minutes. While you scan the sensor yourself with a phone or reader, once you connect to the libreview website, you can download a csv of the full history every 15 minutes.
A sensor can be scanned by any phone, but only 1 phone can be connected to the site to sync the data. I've connect ours to and old phone, so there's a dedicated one available for anyone to scan the sensor. The reader you have to connect to a computer with the provided cable to upload all of the data.
I was hesitant about it's price at first, but it seems to be working pretty well for us. I am doubting the sensor will stay on the the full 14 days. Mitsu has it on her shoulder now, with a little shirt over it to keep her from scratching it off.