The iRig HD is a practical solution to connect an XLR mic to a computer or mobile device. In this way, you can get a higher quality audio than with the average USB mic, without much extra hassle.
The compact size makes it apt to work almost as an adapter. I have the iRig Pre HD attached to my computer to connect a phantom-powered condenser mic for streaming purposes. In this way, I can avoid moving the audio interface from my main recording set-up, and reconnecting it back again.
The audio quality is good for my use case, with no issues or glitches. My mic requires phantom power, and it works well with the iRig Pre using just the power coming through the USB connection (not using the batteries).
The device compatibility seems quite good. I tried multiple devices and all recognized the iRig with no issues (where it was not the case of my other interface).
One important consideration is that the iRig Pre HD needs to be connected to a device in order for the mic audio to reach the headphone out. For example, it cannot be used to connect a mic into the aux in of an amp through the headphone out, even when batteries are used. For that use case, you can use the iRig Pre 2 instead.
The rubber-like plastic and the very light weight makes the construction and finish not to feel very solid. But only time will tell how long it lasts in good condition.