I just used this today.The motor ran with about the same level of noise as others I've used and had plenty of power. I ran liners and shaders and had no issues at all. The needle cartridge depth control is of the click grip type. There wasn't much backlash from click to click. All of the needle cartridges I used for testing fit well and weren't sloppy or too tight.
The body of the pen is thick enough for someone with thicker hands. It may be a bit too big for someone with small hands to handle comfortably for an extended amount of time. Overall I'm happy with the operation and quality of the design and machine work that went into making this. It doesn't look like an inexpensive produced item. It looks like some time and effort went into making it.