Hi Nancy,
 NB> The one thing that has stopped me - the cone thread is not as thick -
 NB> is it strong enough to hold a seam? I had heard that since sergers use
 NB> so many threads together, that is why the cone thread is thinner, and
 NB> it shouldn't be used on a regular sewing machine...
For the most part, cone thread is acceptable for use in regular sewing.
It's equal to the 100% polyester thread that you can buy on specials
like 10 spools for $1.00.  True, it is thinner than something like
cotton covered poly, but I don't think it makes that much of a
difference in most projects.  Most of the cones you see (SureLock,
Maxi-Lock, etc) fall into this grouping.
OTOH, Mettler puts out an overlock thread that seems slightly heavier
than the above mentioned brands.  Before writing to you, I tried
breaking a single length of regular cone thread, a double length of the
same and a single length of the Mettler.  The regular cone thread single
length broke easier than the double or the Mettler.  Since most sewing
is done with 2 threads, even in hand sewing, I wouldn't worry too much
about the strength.  If you are concerned, pay a bit more for the
Mettler.
You do have to be careful to watch for more of a lint build up in your
machine from what I've heard. I've never experienced any problems with
that from using cone thread; it generally comes from whatever fabric I'm
using.
With my old Singer machines, I could never use the cheap threads so I
always bought the cotton covered poly.  I've been using cone thread off
and on in my Pfaff for almost 5 years and haven't had any trouble.  I
did have a problem with cotton covered poly fraying about 18 months ago
when I was hemming some polyester dresses for the high school show
choir.  I had the machine sewing about as fast as I could feed the
fabric (these dresses had a large skirt width) since I was working on a
deadline.  Once I noticed the problem, I slowed down and the thread
behaved better.  I think the fraying came from the speed at which I was
sewing.
I guess what it all boils down to, is that it's mostly a matter of
choice.  Try a cone of the cheaper, try the Mettler and compare to what
you've been using.  Hope this has been a help; it's just what I've
experienced.
Catch you later,
Ruth
Geoworks Ensemble & Professional Point - High performance on a budget!
hafflys@primenet.com    FIDO 1:309/63.2
... I am positive that a definite maybe is probably in order.
--- PPoint 2.00
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