I bought this on my own a while ago after my bluewave get got run through the washing machine (it eventually came back to life BTW, but it took a while).
It is my go to bluetooth dongle for my IEMs at this point.
Out of the box it is somewhat dull sounding, especially compared to the bluewave get. But it has a much quieter noise floor than the get. With enough fiddling with eq and settings, you can get a sound pretty close to the get. The get is smaller, but has less battery life. The controls on the get feel nicer, but the flimsy feeling controls on the ES100 actually hold up to use and abuse better.
It's got pretty good range compared to the competition, but not as good as some over ear BT headphones. It is pretty solid at dealing with interference, and you can fiddle with the buffer in settings to make it gloss over more issues or less via buffering.
The biggest con IMO, and you can read people here complaining about it, is charging it. First, there's the people complaining that it doesn't really charge to 100%. That is correct, and it is in the manual. It aims for the sweet spot of maximizing the lithium battery life. I don't think I have ever seen mine go above 100%. However, that's not all that is going into people's complaints. The designers put in behaviors so you can operate it in headless mode as a DAC via USB. But the logic doesn't know the difference between a charging cable and one with data it seems. And whenever you disconnect USB, it goes into an active loop waiting to pair. Once you unplug it from charging, unless you are using it immediately you need to hold down power long enough to switch the blinking green ring to a a red ring and then off. this is poorly documented in the manual, and before I figure this out, I often charged it up the night before, put it away, and hit the gym the next morning only to find 65% power. It's aggravating, but once you know the issue, pretty easy to control. Another gotcha for wasting power is the app. In general you shouldn't need to run the app if you aren't fiddling with settings as they are saved on the device. If you do, at least on iOS, yo ahve to be careful about exiting the app prior to shutting down or it the app will just re-pair with it when it is in focus, which it will be prior to killing the app. So either turn it off via the app and kill the app, or kill the app and use the power button second. In addition, how fast you chew through the battery is VERY dependent on the settings you choose. However, if you max everything the app warns you is energy inefficient, you can bring it down to about 6hours and change.
-the clip is bulky and near useless. With the weight of a cord hanging off it, it is not going to hold very well. So mine mostly goes in a pocket. It's a clip for letting you hook it on a belt or to keep it from hiding in your pocket, but trying to say put it on the collar of a pullover is going to fail.
-the LED for the mode is dim. works great in the dark, in sunlight, not so much.
-versatile sound profile
-pretty solid app.
-works well with all my IEMs without a dongle.