The MOTU M4 is just incredible for its price.
I upgraded my interface for less than the price of the previous one!
Conversion specs regarding DA are among the best on the market.
A to D follows with a great gain & dynamic range and low noise floor level. Read more
The Loopback feature is pretty handy in different situations.
The Unit is steady, doesn't warm up, knobs are solid...
The screen for metering is actually pretty refined and usable to quickly have a rough idea of where you are at with your levels.
Independent 48V is pretty handy as well following your applications.
I had concerns about the fact that it is USB powered only, but plugged directly into the desktop computer for a few weeks now and haven't experienced any dropouts or anything.
The only thing it might be missing in my opinion (which explains my 4.5 instead of 5/5 rating) are Mute & Mono switches directly on the interface.
But i can't complain at this price it's really an awesome unit which i highly recommend if it suits your needs in terms of I/Os.
If you are looking for a better conversion, you won't find better (at least on D to A) unless you spend at least 5 to 10k.
Also you won't be able to hear a difference at this point unless you have a perfectly treated room with high-end full range monitoring system etc.