I’m using the Libre and like it a lot. I’m planning to get a CGM add-on so I can use it with a smartwatch, but I already have good deal of experience using it with NFC only.
Naturally, I started out with the reader from Abbott. There is also an official smartphone app called LibreLink, but I didn’t see much of an advantage to using it, apart from not having to carry a separate device. The app shows the same thing as the reader, but it does have the advantage of a bigger display which is easier to read. I have since gotten used to scanning with my phone, but at first I found it a little tricky to hit the right spot. The reader has much greater range - you pretty much just have to place it in the right general area and it will work.
The Libre isn’t supposed to require any calibration. I guess this means that it won’t change from day to day, but some drift over the course of two weeks is inevitable unless you get really lucky. For me, this meant that the reported value tended to get lower over time, particularly in the second week. It might show something like 3.2 when I was actually 4.5 according to a fingerstick. Initially, I would do a fingerstick right away whenever the Libre reported anything below 3.9, but I got used to it after a while. I ended up just mentally compensating by adding the difference to the reported number. This works well, but I still find it annoying to see long streaks of a red line that I knew wasn’t really there. Since the difference is small, you could just decide that the Libre value is the one to go by, especially if the meter you use isn’t too accurate anyway.
I wish the Libre would just let the user calibrate by choice like the Dexcom G6 does, but neither the reader nor the LibreLink app allows this. To get around this problem, I started using the third-party app Glimp on my Android phone. Since it’s a third-party app, it doesn’t have access to the secret Abbott algorithm that tries to compensate for the drift. This means that it will actually be less accurate than the reader when used by itself, but if you enter calibration values every now and then, it will use them for calibration.
I have since switched over to XDrip, partly because it can automatically get the values from my Contour Next One over Bluetooth. At first thought that XDrip required a Bluetooth add-on to work with the Libre, but it turns out that it can actually just scan the sensor directly with the phone NFC. You just have to select “LibreAlarm” as the data source. You might be satisfied with just the reader, but if you decide to use a CGM add-on intermittently, it could be nice to have all the data in the same place.
I have noticed the same difference that @glitzabetes mentions. The sensor itself stores the last 8 hours in 15-minute intervals. These are the values that are shown on the graph, which means that it will take a while for the graph to catch up. In addition to the 8-hours log, the sensor also stores the last 15 minutes with an interval of just one minute, which is what the trend arrow is based on. Third-party apps like XDrip will show you these detailed readings as well. I guess the simplified trend arrow view is a user-friendliness thing, but personally I much prefer to just eyeball the graph and figure it out for myself.
@daisymae, you might want to try some kind of holder for the sensor, similar to this one: https://www.ebay.co.uk/itm/303191538528. Some people are actually making these themselves using a 3D printer. The sensor itself is seems essentially waterproof and I’ve never heard of one breaking because of water. Some people even use it for scuba diving. The problem is the tape and there are workarounds for that. For swimming, the Libre might actually be better than a Dexcom. I think @Kaelan mentioned using Dexcom for swimming and that he had to time the 5-minute transmission interval with getting out of the water. With the Libre, you can just scan it at any time.