Feature:
Features. Great instant Amp Modeling with big thumb wheel to turn your selected sound into monster or lullaby. Wish it had more record room at high bit rate, but it still lets you laydown a lot of measures to jam to. That's another thing I like, the jam with yourself or to external inputs. Another great thing is the Bass progression that plays in the Key you select in the Jam feature and rhythm. Lots of other features as in product description. Batteries last, but less with the excellent backlight display. I always use wall power unless at a friends and then batteries last about 6 hours without backlight. Negatives: Control button/knob labeling text too tiny.(I used a WhiteOut pen to label some knobs more clearly. Needs standout mark on G/T/B/V knobs to see where they are set. Clip on carrier is secure, but when put on guitar strap, you can't see the display without twisting it around. Clip on will slide onto waist band or belt but presents the same display problem. (I use a big black office paper clip to hold mine to the edge of a music stand, and leave it there. And I have put velcro on back of PX4 clip-on and the face of my music stand. This arrangement is quite secure. This is brings us to one thing that would be great for this baby... a jack to accept a footswitch to scroll the presets.

Quality:
Made Well? It is plastic, but I swear to you, I have dropped it from table top level at least 10 times and a couple of times it hit the floor when the music stand fell over face first. The case has even popped open. Each time I have thought OMG this has to be the end, but unbelieveablly it keeps right on performing exactly as it did when new. It is beyoud rugged. My only disappointment is the slide selector switches on the sides for Hi/Lo pickup and Off/On/Backlight. These gave up after about a year, but were prob. do to the above mentioned belly flops. I just leave the pickup set at Hi for Humbuckers...and a toothpick or push pin works on the other slider.

Value:
If you are a performer and need hand free switching of presets, this isn't the tool. But for home and garage players this is a very powerful tool and really makes one guitar sound like one thousand other setups. Amps, Cabinets, Pick-ups, Miles of effects, Rhythm,Bass,Tuner,lots more.

Desirability:
I'm not much on needing the coolest look, I want performance and the PX4 has it in a cool package about the size of a cigarette pack.

Sound:
Playin through '74 Fender Twin Reverb, PeaveyBackStagePLus and Gretsch Electromatic. LP Studio and SG. Have only used the PX4 and Digitech RP100 which is fine, but the PX-4 is heads above it. The range of factory presets sound is better and easier to adjust to create your user presets. I've had the PX-4 about 3 years and only used the RP100 a couple of times since and I play at least 1 hour everyday. Take advantage of the Gain,Treble,Bass and Vol adjustments to trim in any of Presets when the venue accoustics change from where you normally set them up. Also there's easy access to clicking through the "change settings" (my term) on any preset, can alter the sound tiny or knock out the walls.

Ease of Use:
This baby has a lot of different levels of adjustment, but after just a little noodling around it mostly becomes automatic and easily adjusted on the fly. The RP-100 mentioned above drove me crazy trying to dial in what I wanted.

Support:
Contacted them about slide switches mentioned above. Helpful, steered me to supplier for parts, but cost+shipping wasn't worth it.

Overall:
If it dies, I will buy another immediately...with the hope Korg includes a footswitch in newer models.

Feature:
plenty of features that make it easy to plug in and play. If you want to sit there and tweak all day, go buy a podxt (I have this for recording, and the Korg for practicing on the couch or when traveling)

Quality:
Light weight and made of plastic, but what isn't these days. I have no plan of stepping on it and I take care of all my equipment anyways.

Sound:
Great sounds W/ a variety of different amps. It is very cool to jam w/ or practice although the volume could be increased just a tad.

Ease of Use:
It has all the sounds I could want and they are extremely easy to dial in.

Support:
have not dealt w/ them.

Overall:
It's a keeper.

Feature:
Possibly to many features for the little unit to handle, quality seems to be less then what Korg previously offered in the old PX units.

Quality:
I returned mine, quality inferior to its predecessors. I purchased the unit because I also own a PX3B bass trainer, and in my opinion the PX3B performs much better for my application. The older unit is cleaner, and the auxiliary record function performs much better/clearer on the old PX3B.

Value:
I was disappointed with the PX4D performance, especially when I own and use daily the PX3B with fantastic results. I ranked its value at 5, not suitable for the discriminating user, but it might make a nice toy for a starter guitar package.

Desirability:
It would be a great product if it performed better, I returned the product.

Sound:
A little to noisy for direct recording, but suitable for practice along with auxiliary source. Some fun tones to noodle around with.

Support:
I didn't need to correspond with Korg, however the store I purchased the unit from contacted them and received a very timely responce.

Overall:
I'll wait until Korg pulls this off the market and see what they come up with next, as I said before, my old PX3B is fantastic so I believe Korg will be able to work out the performace flaws in the PX4D. The thing that I like leastly about the unit, is the quality of the phrase trainer, especially the auxiliary phrase recording feature. Normally when recording a phrase off of a CD (Aux Source) with the PX3B, you simply push the Phrase Trainer button once, "Aux" will appear in the LCD window (if you continue to push the Phrase Trainer button, the other recording source options will appear). Then, with the auxiliary source (CD) playing, you hit the "Enter/Rec" button and after the phrase is recorded you can either hit the button again, which ends the recording and begins looping the recorded phrase, or you can wait until the unit records the maximum measures it's programmed to record and looping begins automatically. When the unit is functioning properly, after the unit has recorded the phrase and the looping of the recorded phrase begins, the Aux source is muted and you only hear the recorded loop, which then you may play along with to learn the phrase. When I attempted to record a phrase off of a CD with the new unit, the recorded phrase is garbled, and the Aux source isn't muted. Of course the simple solution for canceling the Aux source is to hit pause on the CD player, but that doesn't help the fact that the recorded loop is uselessly garbled. Since the phrase trainer function of the unit was the primary function I needed, and the noise level made it inadequate for recording, the combined deficiencies make the PX4D useless to me. But as I implied before, it might make a nice Christmas toy for a beginner to get with their starter guitar/bass package.