Feature:
Most useful features are definitely the compact size and the stereo outputs. The stereo expansion feature is also a good one -- it really "widens" the sound output.

Quality:
I really like the fit/finish and build quality of this amp. The polymaric (truck bedliner) finish has held up well, and I'm confident it will continue to do so. The acoustic cloth covering is no more or less durable than other cloth coverings, so you need to be careful with it, but mine is snag-free after over 6 months of use. Some have purchased custom-made covers for this amp; I think that's a good idea.

Value:
It costs more, but it looks cooler and runs better -- just like most expensive cars, home theater systems, etc. You get what you pay for.

Desirability:
This is a must-have amp if, like me, you have several different keyboard rigs and amplification configurations to choose from and plan with. I use the KP-100S for smaller gigs, or even medium-sized gigs (with a mixer and/or preamp to beef up the sound). For larger gigs, I use something, well, larger (typically a Bose PAS system, or a combo amp/twin full range speaker setup with separate mixer/effects). In some cases in the past, I would play gigs with no onstage keyboard monitor. This was mainly due to space limitations, or travel-related constraints (no room to transport an amp due to air travel or limited van space). This amp is small enough to fit on compact stages or in smaller vehicles, so I can now at least hear myself onstage. For that reason alone, it's a great buy.

Sound:
Excellent sound...for what it is. This is a 38 pound, compact, easy-to-transport amp. It's designed to sound great, but not at really high volume. Actually, if you run your keyboards into a good submixer and/or preamp first, you can really bring out the best in this amp, sonically. For its size, you can't beat it. In fact, for what it's designed for (smaller/lower volume gigs), it gets a "10" in the sound category.

Ease of Use:
Very easy to get a good sound. The bass frequencies drop off pretty dramatically, but it does have a subwoofer output if you need more low end onstage. I like the "component" approach -- where you can bring a powered sub if you need one, but if space is limited or gig volume doesn't demand it, you can travel light and leave the sub at home. This amp has basic, but useful, EQ settings and inputs, too.

Support:
I have been able to get through to John Fisher, the president of the company, and have spoken with his wife (who's operations manager there) on a number of occasions. Both are very helpful, and want to help you sound your best. Motion Sound has gone as far as custom-fabricating parts for me (for my Motion Sound Pro 3t-m), and shipping them quickly for a reasonable rate. This is an excellent company if you're looking for service, support and good advice.

Overall:
I expect that this amp will hold up for many years. I have owned several other motion sound products, and they treat you well as long as you treat them well.

Overall:
Very nice sound but its very VERY quiet for a 50watt amp. I don't expect earth shattering power from a small conbo but I do expect it to compete in volume with a small bass amp and an un miked drum kit. Unfortunately this thig can't without distorting. It can really only be used as a practive amp due to its lack of volume.

Feature:
The amps main feature is it's stereo output which does really help bring keyboard patches to life. It lacks a master volume or any effect send/return features.

Quality:
I took the back off mine and the wiring inside looks a bit on the cheap side, also the power amps have no real heat sink, they're just glued to the rear metal panel.

Value:
If it was louder and had a more effective EQ, it would be a good buy. As it is, I'm disappointed with this product.

Desirability:
I'm planning to sell mine and get something with a more realistic volume for live gigs.

Sound:
The overall sound is good. My main concern is the lack of volume. It's very quite for a twin 50w amp. It can't match volume with similar small guitar and bass combos. Also the effectiveness of the EQ (bass midd treble) is quite limited with only what sounds like a very small change in the frequency of the sound

Ease of Use:
Very just plug in and play. It's lack of features makes use very straight forward

Support:
They're easy to reach and friendly.

Overall:
A great idea, but I think the advertised wattage of this amp is wrong. It's way too quite for gigging and I usually gig in a fairly quite jazz band.