As monitors, these are terrible: No bass, no treble, all mid and even that's a bit fuzzy. However, as *comparisons* next to you main monitors, these are brilliant. Ever wondered what your track would sound like on a mono radio? Use these. Wonder whether you can still make out the lyrics when someone sets your track as their ringtone? Use these. Is your vocal too loud/quiet? Use these to check, then compare back with your main monitors.
The build quality is excellent, though the power supply is a little unusual. They're a lot bigger than you expect too.
In all, I'm really please with these. I used then in conjunction with a pair of ADAM A7x midfields, and have noticed my mixes improve significantly.