Feature:
I originally looked at this for the 12-string simulator. I don't really care for that sound and use another tweaked setting for that sound. When I heard the the rhythm and bass patterns you could play along with (100) and the fact you could select the key--well, that was it--I pulled out the plastic. I've had no regrets. There's a lot to keep you interested and playing your guitar on this thing.

Quality:
I do notice that sometimes, while I'm playing, it loses the setting it's on and goes back to no effects. In that case a push to the next effect and back works.

Value:
It does a lot more than a Fishman Aura. I believe the sound it comparable and it does a LOT more. The Fishmans are guitar specific and don't even have a tuner...and they cost more.

Desirability:
I'd buy another one if it were lost or stolen.

Sound:
I don't know what people are hooking this up to or what kind of cables they are using, or if their house is directly under huge power lines, but I get absolutely no hiss. I'm using shielded cables, but nothing fancy. I'm going guitar--PX4A--Old Peavey stereo mixing board--Mac Garageband and I get no hiss...to just play through headphones, or record. This box truly takes the piezo edge off my acoustic-electric. I don't even bother with additionally mic-ing my acoustic-electric guitar anymore.

Ease of Use:
It's pretty straightforward. Just by the fact that it does a lot of things, well, you have to get to know how to navigate it if you want to utilize it all. Most times I just want to tune up, use a couple of acoustic guitar pre-sets and maybe tweak volume or reverb level, and that's very straightforward.

Support:
Haven't used it.

Overall:
I just have to figure how to have it accessible, yet out of harms way if I do a solo gig. A stomp box may be of more utility in this setting.

Feature:
The reverbs are absolutely fantastic! I am extremely picky about reverb - I refuse to use most reverbs because they make my guitar tone muddy. This is not the case with the PX4A - The reverb sounds are lush without being muddy. There are several reverbs to choose from - I go with ROOM2 - they are all fully adjustable for mix and depth. There are several acoustic guitar modeling EQs to choose from. It is very nice that they gave us BASS, MIDDLE and TREBLE dedicated knob controls on the front of the interface. (I have not tried any of the chorus's or delays yet - so I cant comment there)

Quality:
My only problem with the quality of the unit is in the ON/OFF switch. It feels cheap and I am very careful to treat it with great care.

Value:
I am amazed at how great the sound of this tiny unit is! The reverbs in particular are exquisite! I would have no problem using the reverb for recording or as the main reverb in a high quality PA system. I think it is worth way more than its retail price - a RARE find these days!

Desirability:
It is so tiny! I have it velcro-ed to my guitar.

Sound:
I am using the PX4A with a Yamaha Silent Guitar (nylon) and I am totally thrilled to get such a high quality headphone amp at such a low price! Others who have reviewed this item made note of hiss. I will also note that SOME headphones cause the unit to hiss, but if you experiment with different headphones, you will find that IT DOES NOT HISS with some headphones. I find it works superbly with my Shure E3's, Fostex T-10's, and my favorite headphones to use are my Koss PRO35A's (because they sound great and allow me to hear what is going on in the room). The PX4A makes a loud annoying hiss with my stock Ipod earbuds and my Panasonic earbuds.

Ease of Use:
I found that the interface takes some manual study to figure out how to do things. I was comfortable with the interface after about 10 minutes of playing around and studying the manual. Once you are familiar with the interface, it is easy to adjust the various parameters. I really appreciate having the percussion options, but wish they had put in some conga loops instead of all trap set. You can adjust the level of the drums and cut the bass out if you prefer.

Support:
no experience

Overall:
As long as the ON/OFF button does not break, I expect to happily use it for many years. The only thing that would entice me to replace it is if Korg came out with a newer version that had conga percussion clips. (Plus the jazz percussion clips are pretty corny sounding - more of a shuffle than a jazz swing feel - so I would appreciate if they could upgrade the jazz percussion clips)

Feature:
Has the first 12 string simulation that sounds half way convincing.

Quality:
Seemed to be decently put together.

Value:
Great featureset, but the hiss is a showstopper.

Desirability:
has a built in phrase looper!!!

Sound:
Unfortunately, it emits a great deal of hiss, even with no instrument connected!!! It is unusable for live performance or recording. I tested a second unit, and it emitted the same noise.

Ease of Use:
Straightforward and simple interface.

Support:
Don't know - didn't use it.

Feature:
features is the best part of it. So many that you may get lost the firts times you use it. But the lack of a small, simple, button style pedal to stop working while you are playing, is a serious handicap. If you are playing and want to stop effects but continue playing, you have to stop all and use your hand to bypass it.

Quality:
Hiss can bother you after half an hour of playing. Rest is OK, but this is A SERIOUS HANDICAP.

Value:
Too expensive for a TOY. And this is what it is. A lot of money for having fun at home.

Sound:
Hiss is the greatest problem with this unit. You can