Incredibly Solid Printer
I initially had an older M2 which I recently upgraded to use the v4 hotend. It's a very solid printer that produces some stellar results and had handled every type of filament I've thrown at it. The one caveat is that it isn't quite as user-friendly as something like an Ultimaker or a MakerBot. In particular I find tweaking the bed leveling a bit of a hassle at times, as I have to relevel the bed more often than I would like; though I've read that the newer ones are more reliable in that regard. However, once I've got the settings really "dialed in" I can just hit print and walk away. I'm using Simplify 3D for my slicer, which has profiles for the M2. It's a very powerful and easy-to-use slicer.