I used to have a 60's Kenmore, and I think that one is from the 70's, so it's probably pretty reliable. I doubt too many people have that exact model tho.
Whether I bought it or not would depend on what they're asking for it. Kenmore's don't hold much value unfortunately, so the real value is to the owner. I don't think I'd pay more than $50 for it (possibly only $25), and only if it came with some attachments and the manual.

The only thing that would stop me would be the lack of the "mending zigzag" stitch on some models and a price over $60.00

I just found a 158.12350 for $20.00! I do have to clean and oil, but everything else checked out at the resale store.

I found this review of a very similar machine--also a 158, but the specific model number is a little different, so it might be a tad newer than yours:

http://www.sewinginsight.com/other-brands/kenmore-158-1340-review/

That's what my Kenmore looks like! And I purchased mine in the mid- to early 1980s.

But mine doesn't have the external buttonhole maker that's shown on that review. It does, however, make excellent rectangular buttonholes with a relatively easy setup. Every time I make a buttonhole, I think "why am I always so intimidated by this? It's a snap! Make a trial on a scrap, and off you go!"

My machine is a workhorse. Still going strong, and does everything I need it to. (I do, however, turn my foot pedal around so that I can rest my heel on the hinge instead of on the floor.)

I did sew this weekend on a newer Brother machine, and it had a much smoother operation. But I still really like my Kenmore.

(I'm going to have to look and see what my model number is, exactly.)

Here's a thread from this very forum about Kenmore 158s

http://ths.gardenweb.com/forums/load/sewing/msg090742299792.html?11

But the 158 had a lot of models, because I found this 158 that's a 3/4-size machine!

http://stitchnerd.wordpress.com/2011/06/16/sears-kenmore-158-10401-model-1040-sewing-machine-a-review/

And here are a bunch of people who love their old Kenmores.

I bought that machine maybe 14 yrs ago at a thrift store for $19.99 in perfect working order and still use it today. It was missing the removeable work table but found someone selling the same machine on craigslist and bought just that part for another $20.