Feature:
It has a line out for a sub woofer meaning if you want to add a bass or Cello to your group you can really use the full potential low range of these instruments. Anti feedback is a mystery to me except to say it worked flawlessly. Mute button so you can tune or others can tune without adjusting the volume down which means you set it and forget it.

Quality:
Fit and finish are flawless. This is a discreet box. No one will notice it except for the great sound.

Value:
Relative to the industry standard AER it is well priced I guess.

Desirability:
Discreet powerful, silent ,no buzz or hum when not in use.If I can convince the misses I will purchase the 90 as well as the cheaper 60.

Sound:
My small acoustic trio (2 guitars and a Cello) are looking for a small venue amp to balance the power of the Cello and add a little to our voices. I'm a fairly experienced player of 25 years and currently own a Princeton Chorus. Listening to my friend an excellent guitar player fly through some classic folk songs I was impressed with the clarity and power. Even when we had half volume with a ridiculous amount of sound pressure coming out of the little box we heard every nuance of the guitar.0 distortion even when aggressively attacking the music or slapping.We were very impressed and a little disappointed as the less expensive models we looked at (Laney, Beringer) sounded muddy (god awful)in comparison. My friend is going to purchase the 60 as the 90 has more power than we need. I suggest players go to a dealer who can let them try a variety of amps starting with an AER model to establish a baseline. I felt the Rolland matched the Aer products for less money still I think both are overpriced.The Marshall AS50D (I haven't tested)looks promising as a less expensive alternative.

Ease of Use:
Great playable sound was as easy as plugging in and turning on. However there are a lot of options and features yet to be explored.

Support:
Never dealt with after service.

Overall:
Not a long term owner. After testing our band ordered the smaller 60. I might add illuminated controls , with an on off switch for dark venues. Your instruments and hard work need to be played through a proper amp save your money and invest in a decent amp. Listen to a variety of amps within minutes of each other with similar settings on your guitar.