Feature:
Great sound, bass rolloff, 10 db pad, omni capsule - all for $100 - you cannot beat that. It came with a mic clip, not a shockmount, and that will cost you $35 elsewhere so beware of that. The MXL 41-603 shockmount fits the 604 nicely and is very high quality - better than any other shockmounts I have.

Quality:
Not near as heavy as my SM81 (136 g compared to 230 g for the SM81). It is actually the lightest of my mic collection now but appears well made.

Value:
Great value for a great sound. A low cost "replacement" for an SM81 when you need to mic an acoustic instrument and your SM81 is not available.

Desirability:
Very attractive mic. The grill on the capsules is almost transparent though, and it looks a little odd. But, oh the sound...

Sound:
For acoustic guitar, I love the sound of this mic. It is very close to the SM81 in my side-by-side shootout, using the recorder's faders to go back and forth between mics on lots of different sounding guitar pieces. The mids and highs are bright (but not too bright) and well defined, very much like the SM81. It has a little color (very slight), sounding a little warmer and less sterile, compared to the SM81. The SM81 picks up a more of the nuance secondary tones from my guitar, most of which I like but there are a couple which I would rather not pick up, and the 604 does not pick up those bad ones (nice!). There is a hint less bass in the 604 compared to the SM81, but they're pretty close. The 604 is definitely a lot hotter mike than the SM81 - about twice at hot. I compared specs and the 604's 10 mV/Pa sensitivity spec bears that out (compared to only 5.6 mV/Pa for the SM81). I had a third mic in the shootout (Studio Projects B3) which did not even compare to the SM81 or MXL 604. It has a shrill high end by comparison and the midrange was weak. Its differences to the other two underscored for me how close the SM81 and the MXL 604 are in sound. Biggest differences between MXL 604 and SM81 are 1) the much higher sensitivity in the 604 and 2) the slightly warmer tone (color) of the 604 (not quite as transparent as the SM81).

Ease of Use:
Simple handy switches for rolloff and pad on the mic, and the capsules interchange easily. Very simple and straightforward labels for the switches.

Support:
Have not used it.

Overall:
Very, very nice - I wish it came with a shockmount though, but that would push up the cost.