I'm having a hard time finding much information on the Suzuki KM-88s, which I found quite cheap on Craig's list. I was initially looking for something rather cheap for practicing and possibly for some synth/electronic stuff but if this is higher quality and in a similar price range than I might be interested in it. It was tough just finding a brochure or basic information on it online, much less any user reviews. I can't even find what the "13 instrumental voices" are. Thanks in advance to anyone that knows anything about it.

I have not played the specific model that you mention, but I have played a couple of "baby grand" Suzuki Digital Pianos, one new and one pre-owned, and I personally found them extremely expensive compared to the low quality of sound and action that they delivered.
I would suggest you to try that digital piano before considering buying it.

That is good advice. I am trying to find something in an extremely low price range though (college student). I was hoping to get something aroun $50 that would be at least more than just a toy (like some of those cheap Casios). I then saw this Suzuki though that retails for $600 or so and wondered if I should go a little over my budget for this Suzuki priced down to $150, if it is superior enough to some of the $150-ish Yamaha portable pianos that can be found around $50 from the right seller online or on Craig's list.

The Suzuki KN88 is not an "instrument" I could recommend to anyone. Poor touch, poor tone, poor reliability, IMO. If you want to practice "piano" you need something a lot closer to a piano to practice on.

The technology to emulate an acoustic
piano has been around since at least
the 1970's, and by the 1980's the
digital pianos already performed
similar to the best ones of today.
So now, 20 yrs. later, digital
piano technology is well-established
and widespread, and you would have
a really hard time buying a bad
weighted-key digital piano. Even
the least expensive digitals today
have technology that is superior
to the best digitals of the 1980's
and will perform like an acoustic
piano.

Used digitals are the best value
around. A digital piano is
essentially a computer with a keyboard
and speakers (if you open any
digital piano, all you'll see
inside is a few computer chips
and other electrical components,
connected to the keyboard and
speakers with wires), and, like
pc's, used ones lose value fast.
A ten yr. old dp, like a 10 yr.
old pc, is worth little, maybe
a couple of hundred dollars, but
it will play similar to a brand
new one costing thousands. (Moreover,
a dp from the 1980's, like a
pc from that era, is worth almost
nothing, and you could get it for
$50 or less, and it will play
like an acoustic piano.)

There is a tremendous bias
against Suzuki pianos on these
forums, and people will post all
kinds of lies about their performance
and quality. This Suzuki
digital should be okay. Offer
half price or less when buying
any used digital, and the seller
should grab for that because
that's probably the only offer
he'll get. It's tough to sell
any piano, since the number of
players in the population is
small. Furthermore, there's no
warranty, and there's nowhere
the seller can unload it fast
because a piano dealer won't
buy it, and a pawn shop will
give him almost nothing for it.

Gyro,
Yes, I have a bias against Suzuki digital pianos. It comes from hands on experience with dozens of them over years. My opinions and observations are well founded and I resent you characterizing them as lies.

You sir, display a very consistant bias against anyone spending over $100 for an "instrument." A Suzuki KM88 for $50 will definitely NOT "play like an acoustic piano!"

Your contention that, "by the 1980's the digital pianos already performed similar to the best ones of today." is utter nonsense. The top of the line Roland, Yamaha, or Kawai of even five years ago will not even come close to the performance today of top line models.